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Jbuilder gives you a simple DSL for declaring JSON structures that beats manipulating giant hash structures. This is particularly helpful when the generation process is fraught with conditionals and loops. Here's a simple example:
# app/views/messages/show.json.jbuilder
json.content format_content(@message.content)
json.(@message, :created_at, :updated_at)
json.author do
json.name @message.creator.name.familiar
json.email_address @message.creator.email_address_with_name
json.url url_for(@message.creator, format: :json)
end
if current_user.admin?
json.visitors calculate_visitors(@message)
end
json.comments @message.comments, :content, :created_at
json.attachments @message.attachments do |attachment|
json.filename attachment.filename
json.url url_for(attachment)
end
This will build the following structure:
{
"content": "<p>This is <i>serious</i> monkey business</p>",
"created_at": "2011-10-29T20:45:28-05:00",
"updated_at": "2011-10-29T20:45:28-05:00",
"author": {
"name": "David H.",
"email_address": "'David Heinemeier Hansson' <david@heinemeierhansson.com>",
"url": "http://example.com/users/1-david.json"
},
"visitors": 15,
"comments": [
{ "content": "Hello everyone!", "created_at": "2011-10-29T20:45:28-05:00" },
{ "content": "To you my good sir!", "created_at": "2011-10-29T20:47:28-05:00" }
],
"attachments": [
{ "filename": "forecast.xls", "url": "http://example.com/downloads/forecast.xls" },
{ "filename": "presentation.pdf", "url": "http://example.com/downloads/presentation.pdf" }
]
}
To define attribute and structure names dynamically, use the set!
method:
json.set! :author do
json.set! :name, 'David'
end
# => {"author": { "name": "David" }}
To merge existing hash or array to current context:
hash = { author: { name: "David" } }
json.post do
json.title "Merge HOWTO"
json.merge! hash
end
# => "post": { "title": "Merge HOWTO", "author": { "name": "David" } }
Top level arrays can be handled directly. Useful for index and other collection actions.
# @comments = @post.comments
json.array! @comments do |comment|
next if comment.marked_as_spam_by?(current_user)
json.body comment.body
json.author do
json.first_name comment.author.first_name
json.last_name comment.author.last_name
end
end
# => [ { "body": "great post...", "author": { "first_name": "Joe", "last_name": "Bloe" }} ]
You can also extract attributes from array directly.
# @people = People.all
json.array! @people, :id, :name
# => [ { "id": 1, "name": "David" }, { "id": 2, "name": "Jamie" } ]
To make a plain array without keys, construct and pass in a standard Ruby array.
my_array = %w(David Jamie)
json.people my_array
# => "people": [ "David", "Jamie" ]
You don't always have or need a collection when building an array.
json.people do
json.child! do
json.id 1
json.name 'David'
end
json.child! do
json.id 2
json.name 'Jamie'
end
end
# => { "people": [ { "id": 1, "name": "David" }, { "id": 2, "name": "Jamie" } ] }
Jbuilder objects can be directly nested inside each other. Useful for composing objects.
class Person
# ... Class Definition ... #
def to_builder
Jbuilder.new do |person|
person.(self, :name, :age)
end
end
end
class Company
# ... Class Definition ... #
def to_builder
Jbuilder.new do |company|
company.name name
company.president president.to_builder
end
end
end
company = Company.new('Doodle Corp', Person.new('John Stobs', 58))
company.to_builder.target!
# => {"name":"Doodle Corp","president":{"name":"John Stobs","age":58}}
You can either use Jbuilder stand-alone or directly as an ActionView template language. When required in Rails, you can create views à la show.json.jbuilder (the json is already yielded):
# Any helpers available to views are available to the builder
json.content format_content(@message.content)
json.(@message, :created_at, :updated_at)
json.author do
json.name @message.creator.name.familiar
json.email_address @message.creator.email_address_with_name
json.url url_for(@message.creator, format: :json)
end
if current_user.admin?
json.visitors calculate_visitors(@message)
end
You can use partials as well. The following will render the file views/comments/_comments.json.jbuilder
, and set a local variable comments
with all this message's comments, which you can use inside the partial.
json.partial! 'comments/comments', comments: @message.comments
It's also possible to render collections of partials:
json.array! @posts, partial: 'posts/post', as: :post
# or
json.partial! 'posts/post', collection: @posts, as: :post
# or
json.partial! partial: 'posts/post', collection: @posts, as: :post
# or
json.comments @post.comments, partial: 'comments/comment', as: :comment
The as: :some_symbol
is used with partials. It will take care of mapping the passed in object to a variable for the partial. If the value is a collection either implicitly or explicitly by using the collection:
option, then each value of the collection is passed to the partial as the variable some_symbol
. If the value is a singular object, then the object is passed to the partial as the variable some_symbol
.
Be sure not to confuse the as:
option to mean nesting of the partial. For example:
# Use the default `views/comments/_comment.json.jbuilder`, putting @comment as the comment local variable.
# Note, `comment` attributes are "inlined".
json.partial! @comment, as: :comment
is quite different from:
# comment attributes are nested under a "comment" property
json.comment do
json.partial! "/comments/comment.json.jbuilder", comment: @comment
end
You can pass any objects into partial templates with or without :locals
option.
json.partial! 'sub_template', locals: { user: user }
# or
json.partial! 'sub_template', user: user
You can explicitly make Jbuilder object return null if you want:
json.extract! @post, :id, :title, :content, :published_at
json.author do
if @post.anonymous?
json.null! # or json.nil!
else
json.first_name @post.author_first_name
json.last_name @post.author_last_name
end
end
To prevent Jbuilder from including null values in the output, you can use the ignore_nil!
method:
json.ignore_nil!
json.foo nil
json.bar "bar"
# => { "bar": "bar" }
Fragment caching is supported, it uses Rails.cache
and works like caching in HTML templates:
json.cache! ['v1', @person], expires_in: 10.minutes do
json.extract! @person, :name, :age
end
You can also conditionally cache a block by using cache_if!
like this:
json.cache_if! !admin?, ['v1', @person], expires_in: 10.minutes do
json.extract! @person, :name, :age
end
Aside from that, the :cached
options on collection rendering is available on Rails >= 6.0. This will cache the rendered results effectively using the multi fetch feature.
json.array! @posts, partial: "posts/post", as: :post, cached: true
# or:
json.comments @post.comments, partial: "comments/comment", as: :comment, cached: true
If your collection cache depends on multiple sources (try to avoid this to keep things simple), you can name all these dependencies as part of a block that returns an array:
json.array! @posts, partial: "posts/post", as: :post, cached: -> post { [post, current_user] }
This will include both records as part of the cache key and updating either of them will expire the cache.
Keys can be auto formatted using key_format!
, this can be used to convert keynames from the standard ruby_format to camelCase:
json.key_format! camelize: :lower
json.first_name 'David'
# => { "firstName": "David" }
You can set this globally with the class method key_format
(from inside your environment.rb for example):
Jbuilder.key_format camelize: :lower
By default, key format is not applied to keys of hashes that are passed to methods like set!
, array!
or merge!
. You can opt into deeply transforming these as well:
json.key_format! camelize: :lower
json.deep_format_keys!
json.settings([{some_value: "abc"}])
# => { "settings": [{ "someValue": "abc" }]}
You can set this globally with the class method deep_format_keys
(from inside your environment.rb for example):
Jbuilder.deep_format_keys true
Jbuilder is the work of many contributors. You're encouraged to submit pull requests, propose features and discuss issues.
See CONTRIBUTING.
Author: rails
Source code: https://github.com/rails/jbuilder
License: MIT license
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Install via pip:
$ pip install pytumblr
Install from source:
$ git clone https://github.com/tumblr/pytumblr.git
$ cd pytumblr
$ python setup.py install
A pytumblr.TumblrRestClient
is the object you'll make all of your calls to the Tumblr API through. Creating one is this easy:
client = pytumblr.TumblrRestClient(
'<consumer_key>',
'<consumer_secret>',
'<oauth_token>',
'<oauth_secret>',
)
client.info() # Grabs the current user information
Two easy ways to get your credentials to are:
interactive_console.py
tool (if you already have a consumer key & secret)client.info() # get information about the authenticating user
client.dashboard() # get the dashboard for the authenticating user
client.likes() # get the likes for the authenticating user
client.following() # get the blogs followed by the authenticating user
client.follow('codingjester.tumblr.com') # follow a blog
client.unfollow('codingjester.tumblr.com') # unfollow a blog
client.like(id, reblogkey) # like a post
client.unlike(id, reblogkey) # unlike a post
client.blog_info(blogName) # get information about a blog
client.posts(blogName, **params) # get posts for a blog
client.avatar(blogName) # get the avatar for a blog
client.blog_likes(blogName) # get the likes on a blog
client.followers(blogName) # get the followers of a blog
client.blog_following(blogName) # get the publicly exposed blogs that [blogName] follows
client.queue(blogName) # get the queue for a given blog
client.submission(blogName) # get the submissions for a given blog
Creating posts
PyTumblr lets you create all of the various types that Tumblr supports. When using these types there are a few defaults that are able to be used with any post type.
The default supported types are described below.
We'll show examples throughout of these default examples while showcasing all the specific post types.
Creating a photo post
Creating a photo post supports a bunch of different options plus the described default options * caption - a string, the user supplied caption * link - a string, the "click-through" url for the photo * source - a string, the url for the photo you want to use (use this or the data parameter) * data - a list or string, a list of filepaths or a single file path for multipart file upload
#Creates a photo post using a source URL
client.create_photo(blogName, state="published", tags=["testing", "ok"],
source="https://68.media.tumblr.com/b965fbb2e501610a29d80ffb6fb3e1ad/tumblr_n55vdeTse11rn1906o1_500.jpg")
#Creates a photo post using a local filepath
client.create_photo(blogName, state="queue", tags=["testing", "ok"],
tweet="Woah this is an incredible sweet post [URL]",
data="/Users/johnb/path/to/my/image.jpg")
#Creates a photoset post using several local filepaths
client.create_photo(blogName, state="draft", tags=["jb is cool"], format="markdown",
data=["/Users/johnb/path/to/my/image.jpg", "/Users/johnb/Pictures/kittens.jpg"],
caption="## Mega sweet kittens")
Creating a text post
Creating a text post supports the same options as default and just a two other parameters * title - a string, the optional title for the post. Supports markdown or html * body - a string, the body of the of the post. Supports markdown or html
#Creating a text post
client.create_text(blogName, state="published", slug="testing-text-posts", title="Testing", body="testing1 2 3 4")
Creating a quote post
Creating a quote post supports the same options as default and two other parameter * quote - a string, the full text of the qote. Supports markdown or html * source - a string, the cited source. HTML supported
#Creating a quote post
client.create_quote(blogName, state="queue", quote="I am the Walrus", source="Ringo")
Creating a link post
#Create a link post
client.create_link(blogName, title="I like to search things, you should too.", url="https://duckduckgo.com",
description="Search is pretty cool when a duck does it.")
Creating a chat post
Creating a chat post supports the same options as default and two other parameters * title - a string, the title of the chat post * conversation - a string, the text of the conversation/chat, with diablog labels (no html)
#Create a chat post
chat = """John: Testing can be fun!
Renee: Testing is tedious and so are you.
John: Aw.
"""
client.create_chat(blogName, title="Renee just doesn't understand.", conversation=chat, tags=["renee", "testing"])
Creating an audio post
Creating an audio post allows for all default options and a has 3 other parameters. The only thing to keep in mind while dealing with audio posts is to make sure that you use the external_url parameter or data. You cannot use both at the same time. * caption - a string, the caption for your post * external_url - a string, the url of the site that hosts the audio file * data - a string, the filepath of the audio file you want to upload to Tumblr
#Creating an audio file
client.create_audio(blogName, caption="Rock out.", data="/Users/johnb/Music/my/new/sweet/album.mp3")
#lets use soundcloud!
client.create_audio(blogName, caption="Mega rock out.", external_url="https://soundcloud.com/skrillex/sets/recess")
Creating a video post
Creating a video post allows for all default options and has three other options. Like the other post types, it has some restrictions. You cannot use the embed and data parameters at the same time. * caption - a string, the caption for your post * embed - a string, the HTML embed code for the video * data - a string, the path of the file you want to upload
#Creating an upload from YouTube
client.create_video(blogName, caption="Jon Snow. Mega ridiculous sword.",
embed="http://www.youtube.com/watch?v=40pUYLacrj4")
#Creating a video post from local file
client.create_video(blogName, caption="testing", data="/Users/johnb/testing/ok/blah.mov")
Editing a post
Updating a post requires you knowing what type a post you're updating. You'll be able to supply to the post any of the options given above for updates.
client.edit_post(blogName, id=post_id, type="text", title="Updated")
client.edit_post(blogName, id=post_id, type="photo", data="/Users/johnb/mega/awesome.jpg")
Reblogging a Post
Reblogging a post just requires knowing the post id and the reblog key, which is supplied in the JSON of any post object.
client.reblog(blogName, id=125356, reblog_key="reblog_key")
Deleting a post
Deleting just requires that you own the post and have the post id
client.delete_post(blogName, 123456) # Deletes your post :(
A note on tags: When passing tags, as params, please pass them as a list (not a comma-separated string):
client.create_text(blogName, tags=['hello', 'world'], ...)
Getting notes for a post
In order to get the notes for a post, you need to have the post id and the blog that it is on.
data = client.notes(blogName, id='123456')
The results include a timestamp you can use to make future calls.
data = client.notes(blogName, id='123456', before_timestamp=data["_links"]["next"]["query_params"]["before_timestamp"])
# get posts with a given tag
client.tagged(tag, **params)
This client comes with a nice interactive console to run you through the OAuth process, grab your tokens (and store them for future use).
You'll need pyyaml
installed to run it, but then it's just:
$ python interactive-console.py
and away you go! Tokens are stored in ~/.tumblr
and are also shared by other Tumblr API clients like the Ruby client.
The tests (and coverage reports) are run with nose, like this:
python setup.py test
Author: tumblr
Source Code: https://github.com/tumblr/pytumblr
License: Apache-2.0 license
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In this Python article, let's learn about Mutable and Immutable in Python.
Mutable is a fancy way of saying that the internal state of the object is changed/mutated. So, the simplest definition is: An object whose internal state can be changed is mutable. On the other hand, immutable doesn’t allow any change in the object once it has been created.
Both of these states are integral to Python data structure. If you want to become more knowledgeable in the entire Python Data Structure, take this free course which covers multiple data structures in Python including tuple data structure which is immutable. You will also receive a certificate on completion which is sure to add value to your portfolio.
Mutable is when something is changeable or has the ability to change. In Python, ‘mutable’ is the ability of objects to change their values. These are often the objects that store a collection of data.
Immutable is the when no change is possible over time. In Python, if the value of an object cannot be changed over time, then it is known as immutable. Once created, the value of these objects is permanent.
Objects of built-in type that are mutable are:
Objects of built-in type that are immutable are:
Object mutability is one of the characteristics that makes Python a dynamically typed language. Though Mutable and Immutable in Python is a very basic concept, it can at times be a little confusing due to the intransitive nature of immutability.
In Python, everything is treated as an object. Every object has these three attributes:
While ID and Type cannot be changed once it’s created, values can be changed for Mutable objects.
Check out this free python certificate course to get started with Python.
I believe, rather than diving deep into the theory aspects of mutable and immutable in Python, a simple code would be the best way to depict what it means in Python. Hence, let us discuss the below code step-by-step:
#Creating a list which contains name of Indian cities
cities = [‘Delhi’, ‘Mumbai’, ‘Kolkata’]
# Printing the elements from the list cities, separated by a comma & space
for city in cities:
print(city, end=’, ’)
Output [1]: Delhi, Mumbai, Kolkata
#Printing the location of the object created in the memory address in hexadecimal format
print(hex(id(cities)))
Output [2]: 0x1691d7de8c8
#Adding a new city to the list cities
cities.append(‘Chennai’)
#Printing the elements from the list cities, separated by a comma & space
for city in cities:
print(city, end=’, ’)
Output [3]: Delhi, Mumbai, Kolkata, Chennai
#Printing the location of the object created in the memory address in hexadecimal format
print(hex(id(cities)))
Output [4]: 0x1691d7de8c8
The above example shows us that we were able to change the internal state of the object ‘cities’ by adding one more city ‘Chennai’ to it, yet, the memory address of the object did not change. This confirms that we did not create a new object, rather, the same object was changed or mutated. Hence, we can say that the object which is a type of list with reference variable name ‘cities’ is a MUTABLE OBJECT.
Let us now discuss the term IMMUTABLE. Considering that we understood what mutable stands for, it is obvious that the definition of immutable will have ‘NOT’ included in it. Here is the simplest definition of immutable– An object whose internal state can NOT be changed is IMMUTABLE.
Again, if you try and concentrate on different error messages, you have encountered, thrown by the respective IDE; you use you would be able to identify the immutable objects in Python. For instance, consider the below code & associated error message with it, while trying to change the value of a Tuple at index 0.
#Creating a Tuple with variable name ‘foo’
foo = (1, 2)
#Changing the index[0] value from 1 to 3
foo[0] = 3
TypeError: 'tuple' object does not support item assignment
Once again, a simple code would be the best way to depict what immutable stands for. Hence, let us discuss the below code step-by-step:
#Creating a Tuple which contains English name of weekdays
weekdays = ‘Sunday’, ‘Monday’, ‘Tuesday’, ‘Wednesday’, ‘Thursday’, ‘Friday’, ‘Saturday’
# Printing the elements of tuple weekdays
print(weekdays)
Output [1]: (‘Sunday’, ‘Monday’, ‘Tuesday’, ‘Wednesday’, ‘Thursday’, ‘Friday’, ‘Saturday’)
#Printing the location of the object created in the memory address in hexadecimal format
print(hex(id(weekdays)))
Output [2]: 0x1691cc35090
#tuples are immutable, so you cannot add new elements, hence, using merge of tuples with the # + operator to add a new imaginary day in the tuple ‘weekdays’
weekdays += ‘Pythonday’,
#Printing the elements of tuple weekdays
print(weekdays)
Output [3]: (‘Sunday’, ‘Monday’, ‘Tuesday’, ‘Wednesday’, ‘Thursday’, ‘Friday’, ‘Saturday’, ‘Pythonday’)
#Printing the location of the object created in the memory address in hexadecimal format
print(hex(id(weekdays)))
Output [4]: 0x1691cc8ad68
This above example shows that we were able to use the same variable name that is referencing an object which is a type of tuple with seven elements in it. However, the ID or the memory location of the old & new tuple is not the same. We were not able to change the internal state of the object ‘weekdays’. The Python program manager created a new object in the memory address and the variable name ‘weekdays’ started referencing the new object with eight elements in it. Hence, we can say that the object which is a type of tuple with reference variable name ‘weekdays’ is an IMMUTABLE OBJECT.
Also Read: Understanding the Exploratory Data Analysis (EDA) in Python
Where can you use mutable and immutable objects:
Mutable objects can be used where you want to allow for any updates. For example, you have a list of employee names in your organizations, and that needs to be updated every time a new member is hired. You can create a mutable list, and it can be updated easily.
Immutability offers a lot of useful applications to different sensitive tasks we do in a network centred environment where we allow for parallel processing. By creating immutable objects, you seal the values and ensure that no threads can invoke overwrite/update to your data. This is also useful in situations where you would like to write a piece of code that cannot be modified. For example, a debug code that attempts to find the value of an immutable object.
Watch outs: Non transitive nature of Immutability:
OK! Now we do understand what mutable & immutable objects in Python are. Let’s go ahead and discuss the combination of these two and explore the possibilities. Let’s discuss, as to how will it behave if you have an immutable object which contains the mutable object(s)? Or vice versa? Let us again use a code to understand this behaviour–
#creating a tuple (immutable object) which contains 2 lists(mutable) as it’s elements
#The elements (lists) contains the name, age & gender
person = (['Ayaan', 5, 'Male'], ['Aaradhya', 8, 'Female'])
#printing the tuple
print(person)
Output [1]: (['Ayaan', 5, 'Male'], ['Aaradhya', 8, 'Female'])
#printing the location of the object created in the memory address in hexadecimal format
print(hex(id(person)))
Output [2]: 0x1691ef47f88
#Changing the age for the 1st element. Selecting 1st element of tuple by using indexing [0] then 2nd element of the list by using indexing [1] and assigning a new value for age as 4
person[0][1] = 4
#printing the updated tuple
print(person)
Output [3]: (['Ayaan', 4, 'Male'], ['Aaradhya', 8, 'Female'])
#printing the location of the object created in the memory address in hexadecimal format
print(hex(id(person)))
Output [4]: 0x1691ef47f88
In the above code, you can see that the object ‘person’ is immutable since it is a type of tuple. However, it has two lists as it’s elements, and we can change the state of lists (lists being mutable). So, here we did not change the object reference inside the Tuple, but the referenced object was mutated.
Also Read: Real-Time Object Detection Using TensorFlow
Same way, let’s explore how it will behave if you have a mutable object which contains an immutable object? Let us again use a code to understand the behaviour–
#creating a list (mutable object) which contains tuples(immutable) as it’s elements
list1 = [(1, 2, 3), (4, 5, 6)]
#printing the list
print(list1)
Output [1]: [(1, 2, 3), (4, 5, 6)]
#printing the location of the object created in the memory address in hexadecimal format
print(hex(id(list1)))
Output [2]: 0x1691d5b13c8
#changing object reference at index 0
list1[0] = (7, 8, 9)
#printing the list
Output [3]: [(7, 8, 9), (4, 5, 6)]
#printing the location of the object created in the memory address in hexadecimal format
print(hex(id(list1)))
Output [4]: 0x1691d5b13c8
As an individual, it completely depends upon you and your requirements as to what kind of data structure you would like to create with a combination of mutable & immutable objects. I hope that this information will help you while deciding the type of object you would like to select going forward.
Before I end our discussion on IMMUTABILITY, allow me to use the word ‘CAVITE’ when we discuss the String and Integers. There is an exception, and you may see some surprising results while checking the truthiness for immutability. For instance:
#creating an object of integer type with value 10 and reference variable name ‘x’
x = 10
#printing the value of ‘x’
print(x)
Output [1]: 10
#Printing the location of the object created in the memory address in hexadecimal format
print(hex(id(x)))
Output [2]: 0x538fb560
#creating an object of integer type with value 10 and reference variable name ‘y’
y = 10
#printing the value of ‘y’
print(y)
Output [3]: 10
#Printing the location of the object created in the memory address in hexadecimal format
print(hex(id(y)))
Output [4]: 0x538fb560
As per our discussion and understanding, so far, the memory address for x & y should have been different, since, 10 is an instance of Integer class which is immutable. However, as shown in the above code, it has the same memory address. This is not something that we expected. It seems that what we have understood and discussed, has an exception as well.
Quick check – Python Data Structures
Tuples are immutable and hence cannot have any changes in them once they are created in Python. This is because they support the same sequence operations as strings. We all know that strings are immutable. The index operator will select an element from a tuple just like in a string. Hence, they are immutable.
Like all, there are exceptions in the immutability in python too. Not all immutable objects are really mutable. This will lead to a lot of doubts in your mind. Let us just take an example to understand this.
Consider a tuple ‘tup’.
Now, if we consider tuple tup = (‘GreatLearning’,[4,3,1,2]) ;
We see that the tuple has elements of different data types. The first element here is a string which as we all know is immutable in nature. The second element is a list which we all know is mutable. Now, we all know that the tuple itself is an immutable data type. It cannot change its contents. But, the list inside it can change its contents. So, the value of the Immutable objects cannot be changed but its constituent objects can. change its value.
Mutable Object | Immutable Object |
State of the object can be modified after it is created. | State of the object can’t be modified once it is created. |
They are not thread safe. | They are thread safe |
Mutable classes are not final. | It is important to make the class final before creating an immutable object. |
list, dictionary, set, user-defined classes.
int, float, decimal, bool, string, tuple, range.
Lists in Python are mutable data types as the elements of the list can be modified, individual elements can be replaced, and the order of elements can be changed even after the list has been created.
(Examples related to lists have been discussed earlier in this blog.)
Tuple and list data structures are very similar, but one big difference between the data types is that lists are mutable, whereas tuples are immutable. The reason for the tuple’s immutability is that once the elements are added to the tuple and the tuple has been created; it remains unchanged.
A programmer would always prefer building a code that can be reused instead of making the whole data object again. Still, even though tuples are immutable, like lists, they can contain any Python object, including mutable objects.
A set is an iterable unordered collection of data type which can be used to perform mathematical operations (like union, intersection, difference etc.). Every element in a set is unique and immutable, i.e. no duplicate values should be there, and the values can’t be changed. However, we can add or remove items from the set as the set itself is mutable.
Strings are not mutable in Python. Strings are a immutable data types which means that its value cannot be updated.
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Original article source at: https://www.mygreatlearning.com
1659202980
Jbuilder gives you a simple DSL for declaring JSON structures that beats manipulating giant hash structures. This is particularly helpful when the generation process is fraught with conditionals and loops. Here's a simple example:
# app/views/messages/show.json.jbuilder
json.content format_content(@message.content)
json.(@message, :created_at, :updated_at)
json.author do
json.name @message.creator.name.familiar
json.email_address @message.creator.email_address_with_name
json.url url_for(@message.creator, format: :json)
end
if current_user.admin?
json.visitors calculate_visitors(@message)
end
json.comments @message.comments, :content, :created_at
json.attachments @message.attachments do |attachment|
json.filename attachment.filename
json.url url_for(attachment)
end
This will build the following structure:
{
"content": "<p>This is <i>serious</i> monkey business</p>",
"created_at": "2011-10-29T20:45:28-05:00",
"updated_at": "2011-10-29T20:45:28-05:00",
"author": {
"name": "David H.",
"email_address": "'David Heinemeier Hansson' <david@heinemeierhansson.com>",
"url": "http://example.com/users/1-david.json"
},
"visitors": 15,
"comments": [
{ "content": "Hello everyone!", "created_at": "2011-10-29T20:45:28-05:00" },
{ "content": "To you my good sir!", "created_at": "2011-10-29T20:47:28-05:00" }
],
"attachments": [
{ "filename": "forecast.xls", "url": "http://example.com/downloads/forecast.xls" },
{ "filename": "presentation.pdf", "url": "http://example.com/downloads/presentation.pdf" }
]
}
To define attribute and structure names dynamically, use the set!
method:
json.set! :author do
json.set! :name, 'David'
end
# => {"author": { "name": "David" }}
To merge existing hash or array to current context:
hash = { author: { name: "David" } }
json.post do
json.title "Merge HOWTO"
json.merge! hash
end
# => "post": { "title": "Merge HOWTO", "author": { "name": "David" } }
Top level arrays can be handled directly. Useful for index and other collection actions.
# @comments = @post.comments
json.array! @comments do |comment|
next if comment.marked_as_spam_by?(current_user)
json.body comment.body
json.author do
json.first_name comment.author.first_name
json.last_name comment.author.last_name
end
end
# => [ { "body": "great post...", "author": { "first_name": "Joe", "last_name": "Bloe" }} ]
You can also extract attributes from array directly.
# @people = People.all
json.array! @people, :id, :name
# => [ { "id": 1, "name": "David" }, { "id": 2, "name": "Jamie" } ]
To make a plain array without keys, construct and pass in a standard Ruby array.
my_array = %w(David Jamie)
json.people my_array
# => "people": [ "David", "Jamie" ]
You don't always have or need a collection when building an array.
json.people do
json.child! do
json.id 1
json.name 'David'
end
json.child! do
json.id 2
json.name 'Jamie'
end
end
# => { "people": [ { "id": 1, "name": "David" }, { "id": 2, "name": "Jamie" } ] }
Jbuilder objects can be directly nested inside each other. Useful for composing objects.
class Person
# ... Class Definition ... #
def to_builder
Jbuilder.new do |person|
person.(self, :name, :age)
end
end
end
class Company
# ... Class Definition ... #
def to_builder
Jbuilder.new do |company|
company.name name
company.president president.to_builder
end
end
end
company = Company.new('Doodle Corp', Person.new('John Stobs', 58))
company.to_builder.target!
# => {"name":"Doodle Corp","president":{"name":"John Stobs","age":58}}
You can either use Jbuilder stand-alone or directly as an ActionView template language. When required in Rails, you can create views à la show.json.jbuilder (the json is already yielded):
# Any helpers available to views are available to the builder
json.content format_content(@message.content)
json.(@message, :created_at, :updated_at)
json.author do
json.name @message.creator.name.familiar
json.email_address @message.creator.email_address_with_name
json.url url_for(@message.creator, format: :json)
end
if current_user.admin?
json.visitors calculate_visitors(@message)
end
You can use partials as well. The following will render the file views/comments/_comments.json.jbuilder
, and set a local variable comments
with all this message's comments, which you can use inside the partial.
json.partial! 'comments/comments', comments: @message.comments
It's also possible to render collections of partials:
json.array! @posts, partial: 'posts/post', as: :post
# or
json.partial! 'posts/post', collection: @posts, as: :post
# or
json.partial! partial: 'posts/post', collection: @posts, as: :post
# or
json.comments @post.comments, partial: 'comments/comment', as: :comment
The as: :some_symbol
is used with partials. It will take care of mapping the passed in object to a variable for the partial. If the value is a collection either implicitly or explicitly by using the collection:
option, then each value of the collection is passed to the partial as the variable some_symbol
. If the value is a singular object, then the object is passed to the partial as the variable some_symbol
.
Be sure not to confuse the as:
option to mean nesting of the partial. For example:
# Use the default `views/comments/_comment.json.jbuilder`, putting @comment as the comment local variable.
# Note, `comment` attributes are "inlined".
json.partial! @comment, as: :comment
is quite different from:
# comment attributes are nested under a "comment" property
json.comment do
json.partial! "/comments/comment.json.jbuilder", comment: @comment
end
You can pass any objects into partial templates with or without :locals
option.
json.partial! 'sub_template', locals: { user: user }
# or
json.partial! 'sub_template', user: user
You can explicitly make Jbuilder object return null if you want:
json.extract! @post, :id, :title, :content, :published_at
json.author do
if @post.anonymous?
json.null! # or json.nil!
else
json.first_name @post.author_first_name
json.last_name @post.author_last_name
end
end
To prevent Jbuilder from including null values in the output, you can use the ignore_nil!
method:
json.ignore_nil!
json.foo nil
json.bar "bar"
# => { "bar": "bar" }
Fragment caching is supported, it uses Rails.cache
and works like caching in HTML templates:
json.cache! ['v1', @person], expires_in: 10.minutes do
json.extract! @person, :name, :age
end
You can also conditionally cache a block by using cache_if!
like this:
json.cache_if! !admin?, ['v1', @person], expires_in: 10.minutes do
json.extract! @person, :name, :age
end
Aside from that, the :cached
options on collection rendering is available on Rails >= 6.0. This will cache the rendered results effectively using the multi fetch feature.
json.array! @posts, partial: "posts/post", as: :post, cached: true
# or:
json.comments @post.comments, partial: "comments/comment", as: :comment, cached: true
If your collection cache depends on multiple sources (try to avoid this to keep things simple), you can name all these dependencies as part of a block that returns an array:
json.array! @posts, partial: "posts/post", as: :post, cached: -> post { [post, current_user] }
This will include both records as part of the cache key and updating either of them will expire the cache.
Keys can be auto formatted using key_format!
, this can be used to convert keynames from the standard ruby_format to camelCase:
json.key_format! camelize: :lower
json.first_name 'David'
# => { "firstName": "David" }
You can set this globally with the class method key_format
(from inside your environment.rb for example):
Jbuilder.key_format camelize: :lower
By default, key format is not applied to keys of hashes that are passed to methods like set!
, array!
or merge!
. You can opt into deeply transforming these as well:
json.key_format! camelize: :lower
json.deep_format_keys!
json.settings([{some_value: "abc"}])
# => { "settings": [{ "someValue": "abc" }]}
You can set this globally with the class method deep_format_keys
(from inside your environment.rb for example):
Jbuilder.deep_format_keys true
Jbuilder is the work of many contributors. You're encouraged to submit pull requests, propose features and discuss issues.
See CONTRIBUTING.
Author: rails
Source code: https://github.com/rails/jbuilder
License: MIT license
1659396000
Humidifier is a ruby tool for managing AWS CloudFormation stacks. You can use it to build and manage stacks programmatically or you can use it as a command line tool to manage stacks through configuration files.
Add this line to your application's Gemfile:
gem 'humidifier'
And then execute:
$ bundle
Or install it yourself as:
$ gem install humidifier
Stacks are represented by the Humidifier::Stack
class. You can set any of the top-level JSON attributes (such as name
and description
) through the initializer.
Resources are represented by an exact mapping from AWS
resource names to Humidifier
resources names (e.g. AWS::EC2::Instance
becomes Humidifier::EC2::Instance
). Resources have accessors for each JSON attribute. Each attribute can also be set through the initialize
, update
, and update_attribute
methods.
The below example will create a stack with two resources, a loader balancer and an auto scaling group. It then deploys the new stack and pauses execution until the stack is finished being created.
stack = Humidifier::Stack.new(name: 'Example-Stack')
stack.add(
'LoaderBalancer',
Humidifier::ElasticLoadBalancing::LoadBalancer.new(
scheme: 'internal',
listeners: [
{
load_balancer_port: 80,
protocol: 'http',
instance_port: 80,
instance_protocol: 'http'
}
]
)
)
stack.add(
'AutoScalingGroup',
Humidifier::AutoScaling::AutoScalingGroup.new(
min_size: '1',
max_size: '20',
availability_zones: ['us-east-1a'],
load_balancer_names: [Humidifier.ref('LoadBalancer')]
)
)
stack.deploy_and_wait
Once stacks have the appropriate resources, you can query AWS to handle all stack CRUD operations. The operations themselves are intuitively named (i.e. #create
, #update
, #delete
). There are also convenience methods for validating a stack body (#valid?
), checking the existence of a stack (#exists?
), and creating or updating based on existence (#deploy
).
There are additionally four functions on Humidifier::Stack
that support waiting for execution in AWS to finish. They all have non-blocking corollaries, and are named after them. They are: #create_and_wait
, #update_and_wait
, #delete_and_wait
, and #deploy_and_wait
.
You can use CFN intrinsic functions and references using Humidifier.fn.[name]
and Humidifier.ref
. They will build appropriate structures that know how to be dumped to CFN syntax.
Instead of immediately pushing your changes to CloudFormation, Humidifier also supports change sets. Change sets are a powerful feature that allow you to see the changes that will be made before you make them. To read more about change sets see the announcement article. To use them in Humidifier, Humidifier::Stack
has the #create_change_set
and #deploy_change_set
methods. The #create_change_set
method will create a change set on the stack. The #deploy_change_set
method will create a change set if the stack currently exists, and otherwise will create the stack.
To see the template body, you can check the #to_cf
method on stacks, resources, fns, and refs. All of them will output a hash of what will be uploaded (except the stack, which will output a string representation).
Humidifier itself contains a registry of all possible resources that it supports. You can access it with Humidifier::registry
which is a hash of AWS resource name pointing to the class.
Resources have an ::aws_name
method to see how AWS references them. They also contain a ::props
method that contains a hash of the name that Humidifier uses to reference the prop pointing to the appropriate prop object.
When templates are especially large (larger than 51,200 bytes), they cannot be uploaded directly through the AWS SDK. You can configure Humidifier
to seamlessly upload the templates to S3 and reference them using an S3 URL instead by:
Humidifier.configure do |config|
config.s3_bucket = 'my.s3.bucket'
config.s3_prefix = 'my-prefix/' # optional
end
You can force a stack to upload its template to S3 regardless of the size of the template. This is a useful option if you're going to be deploying multiple copies of a template or if you want a backup. You can set this option on a per-stack basis:
stack.deploy(force_upload: true)
or globally, by setting the configuration option:
Humidifier.configure do |config|
config.force_upload = true
end
Humidifier
can also be used as a CLI for managing resources through configuration files. For a step-by-step guide, read on, but if you'd like to see a working example, check out the example directory.
To get started, build a ruby script (for example humidifier
) that executes the Humidifier::CLI
class, like so:
#!/usr/bin/env ruby
require 'humidifier'
Humidifier.configure do |config|
# optional, defaults to the current working directory, so that all of the
# directories from the location that you run the CLI are assumed to contain
# resource specifications
config.stack_path = 'stacks'
# optional, a default prefix to use before deploying to AWS
config.stack_prefix = 'humidifier-'
# specifies that `users.yml` files contain specifications for `AWS::IAM::User`
# resources
config.map :users, to: 'IAM::User'
end
Humidifier::CLI.start(ARGV)
Inside of the stacks
directory configured above, create a subdirectory for each CloudFormation stack that you want to deploy. With the above configuration, we can create YAML files in the form of users.yml
for each stack, which will specify IAM users to create. The file format looks like the below:
EngUser:
path: /humidifier/
user_name: EngUser
groups:
- Engineering
- Testing
- Deployment
AdminUser:
path: /humidifier/
user_name: AdminUser
groups:
- Management
- Administration
The top-level keys are the logical resource names that will be displayed in the CloudFormation screen. They point to a map of key/value pairs that will be passed on to humidifier
. Any humidifier
(and therefore any CloudFormation) attribute may be specified. For more information on CloudFormation templates and which attributes may be specified, see both the humidifier
docs and the CloudFormation docs.
Oftentimes, specifying these attributes can become repetitive, e.g., each user should automatically receive the same "path" attribute. Other times, you may want custom logic to execute depending on which AWS environment you're running in. Finally, you may want to reference resources in the same or other stacks.
Humidifier
's solution for this is to allow customized "mapper" classes to take the user-provided attributes and transform them into the attributes that CloudFormation expects. Consider the following example for mapping a user:
class UserMapper < Humidifier::Config::Mapper
GROUPS = {
'eng' => %w[Engineering Testing Deployment],
'admin' => %w[Management Administration]
}
defaults do |logical_name|
{ path: '/humidifier/', user_name: logical_name }
end
attribute :group do |group|
groups = GROUPS[group]
groups.any? ? { groups: GROUPS[group] } : {}
end
end
Humidifier.configure do |config|
config.map :users, to: 'IAM::User', using: UserMapper
end
This means that by default, all entries in the users.yml
files will get a /humidifier/
path, the user_name
attribute will be set based on the logical name that was provided for the resource, and you can additionally specify a group
attribute, even though it is not native to CloudFormation. With this group
attribute, it will actually map to the groups
attribute that CloudFormation expects.
With this new mapper in place, we can simplify our YAML file to:
EngUser:
group: eng
AdminUser:
group: admin
Now that you've configured your CLI, your resources, and your mappers, you can use the CLI to display, validate, and deploy your infrastructure to CloudFormation. Run your script without any arguments to get the help message and explanations for each command.
Each command has an --aws-profile
(or -p
) option for specifying which profile to authenticate against when querying AWS. You should ensure that this profile has the correct permissions for creating whatever resources are going to part of your stack. You can also rely on the AWS_*
environment variables, or the EC2 instance profile if you're deploying from an instance. For more information, see the AWS docs under the "Configuration" section.
Below are the list of commands and some of their options.
change [?stack]
Creates a change set for either the specified stack or all stacks in the repo. The change set represents the changes between what is currently deployed versus the resources represented by the configuration.
deploy [?stack] [*parameters]
Creates or updates (depending on if the stack already exists) one or all stacks in the repo.
The deploy
command also allows a --prefix
command line argument that will override the default prefix (if one is configured) for the stack that is being deployed. This is especially useful when you're deploying multiple copies of the same stack (for instance, multiple autoscaling groups) that have different purposes or semantically mean newer versions of resources.
display [stack] [?pattern]
Displays the specified stack in JSON format on the command line. If you optionally pass a pattern argument, it will filter the resources down to just ones whose names match the given pattern.
stacks
Displays the names of all of the stacks that humidifier
is managing.
upgrade
Downloads the latest CloudFormation resource specification. Periodically AWS will update the file that humidifier
is based on, in which case the attributes of the resources that were changed could change. This gem usually stays relatively in sync, but if you need to use the latest specs and this gem has not yet released a new version containing them, then you can run this command to download the latest specs onto your system.
upload [?stack]
Upload one or all stacks in the repo to S3 for reference later. Note that this must be combined with the humidifier
s3_bucket
configuration option.
validate [?stack]
Validate that one or all stacks in the repo are properly configured and using values that CloudFormation understands.
version
Output the version of Humidifier
as well as the version of the CloudFormation resource specification that you are using.
CloudFormation template parameters can be specified by having a special parameters.yml
file in your stack directory. This file should contain a YAML-encoded object whose keys are the names of the parameters and whose values are the parameter configuration (using the same underscore paradigm as humidifier
resources for specifying configuration).
You can pass values to the CLI deploy command after the stack name on the command line as in:
humidifier deploy foobar Param1=Foo Param2=Bar
Those parameters will get passed in as values when the stack is deployed.
A couple of convenient shortcuts are built into humidifier
so that writing templates and mappers both can be more concise.
There are a lot of properties in the AWS CloudFormation resource specification that are simply pointers to other entities within the AWS ecosystem. For example, an AWS::EC2::VPCGatewayAttachment
entity has a VpcId
property that represents the ID of the associated AWS::EC2::VPC
.
Because this pattern is so common, humidifier
detects all properties ending in Id
and allows you to specify them without the suffix. If you choose to use this format, humidifier
will automatically turn that value into a CloudFormation resource reference.
A lot of the time, mappers that you create will not be overly complicated, especially if you're using automatic id properties. So, the config.map
method optionally takes a block, and allows you to specify the mapper inline. This is recommended for mappers that aren't too complicated as to warrant their own class (for instance, for testing purposes). An example of this using the UserMapper
from above is below:
Humidifier.configure do |config|
config.map :users, to: 'IAM::User' do
GROUPS = {
'eng' => %w[Engineering Testing Deployment],
'admin' => %w[Management Administration]
}
defaults do |logical_name|
{ path: '/humidifier/', user_name: logical_name }
end
attribute :group do |group|
groups = GROUPS[group]
groups.any? ? { groups: GROUPS[group] } : {}
end
end
end
AWS allows cross-stack references through the intrinsic Fn::ImportValue
function. You can take advantage of this with humidifier
by using the export: true
option on resources in your stacks. For instance, if in one stack you have a subnet that you need to reference in another, you could (stacks/vpc/subnets.yml
):
ProductionPrivateSubnet2a:
vpc: ProductionVPC
cidr_block: 10.0.0.0/19
availability_zone: us-west-2a
export: true
ProductionPrivateSubnet2b:
vpc: ProductionVPC
cidr_block: 10.0.64.0/19
availability_zone: us-west-2b
export: true
ProductionPrivateSubnet2c:
vpc: ProductionVPC
cidr_block: 10.0.128.0/19
availability_zone: us-west-2c
export: true
And then in another stack, you could reference those values (stacks/rds/db_subnets_groups.yml
):
ProductionDBSubnetGroup:
db_subnet_group_description: Production DB private subnet group
subnets:
- ProductionPrivateSubnet2a
- ProductionPrivateSubnet2b
- ProductionPrivateSubnet2c
Within the configuration, you would specify to use the Fn::ImportValue
function like so:
Humidifier.configure do |config|
config.stack_path = 'stacks'
config.map :subnets, to: 'EC2::Subnet'
config.map :db_subnet_groups, to: 'RDS::DBSubnetGroup' do
attribute :subnets do |subnet_names|
subnet_ids =
subnet_names.map do |subnet_name|
Humidifier.fn.import_value(subnet_name)
end
{ subnet_ids: subnet_ids }
end
end
end
If you specify export: true
it will by default export a reference to the resource listed in the stack. You can also choose to export a different attribute by specifying the attribute as the value to export. For example, if we were creating instance profiles and wanted to export the Arn
so that it could be referenced by an instance later, we could:
APIRoleInstanceProfile:
depends_on: APIRole
roles:
- APIRole
export: Arn
To get started, ensure you have ruby installed, version 2.4 or later. From there, install the bundler
gem: gem install bundler
and then bundle install
in the root of the repository.
The default rake task runs the tests. Styling is governed by rubocop. The docs are generated with yard. To run all three of these, run:
$ bundle exec rake
$ bundle exec rubocop
$ bundle exec rake yard
The specs pulled from the CFN docs is saved to CloudFormationResourceSpecification.json
. You can update it by running bundle exec rake specs
. This script will pull down the latest resource specification to be used with Humidifier.
Bug reports and pull requests are welcome on GitHub at https://github.com/kddnewton/humidifier.
The gem is available as open source under the terms of the MIT License.
Author: kddnewton
Source code: https://github.com/kddnewton/humidifier
License: MIT license
1625637060
In this video, we work with JSONs, which are a common data format for most web services (i.e. APIs). Thank you for watching and happy coding!
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