Synchronous Way to Work with Asynchronous Code.

In _Kotlin coroutines tips and tricks _series we are going to solve common real-life issues that might appear when coroutines are used in the code.

TL;DR
Wrap callbacks for asynchronous code with suspendCancellableCoroutine; code examples are available at the end of each chapter.

After playing around with Kotlin coroutines there is a good chance that you have encountered the following dilemma:

  • Writing suspend function.
  • Calling 3rd party asynchronous code that requires callback object with methods such as onSuccess and onFailure .
  • Needing results from callback to continue coroutine execution.

You probably already see the problem here, but let’s highlight it once again — we require results from _asynchronous _code within a synchronous block. Let’s take a look at the real-life example in the following section.

Example: Consuming purchased items using Google Billing API

Imagine we’re selling magic potions in our app that can be bought once at a time. Each time magic potion is purchased via Google Play Billing API it needs to be consumed in order to be available for repetitive purchase.

Per Billing API documentation, the developer must call [consumeAync(](https://developer.android.com/reference/com/android/billingclient/api/BillingClient#consumeAsync)``) and provide an implementation of [ConsumeResponseListener](https://developer.android.com/reference/com/android/billingclient/api/ConsumeResponseListener).

ConsumeResponseListener object handles the result of the consumption operation. You can override the _onConsumeResponse()_ method of the ConsumeResponseListener interface, which the Google Play Billing Library calls when the operation is complete.

In order to notify our user that their magic potion was successfully added to the inventory, we need to check if Billing API has consumed purchased item. Let’s create an initial code draft

import com.android.billingclient.*;

	/**
	  * Consumes provided item
	  * @param billingClient initialized billing client
	  * @param consumerParams consume parameters with purchase token
	  * @return true if purchase is consumed, false otherwise
	 **/
	suspend fun consumeItem(
	 billingClient: BillingClient,
	 consumeParams: ConsumeParams
	): Boolean{
	  // Final result of consumption
	  var isConsumed: Boolean = false
	  // Consumption callback that will be called once Billing API finishes processing
	  val consumeResponseListener = ConsumeResponseListener { billingResult: BillingResult, purchaseToken: String ->
	     isConsumed = billingResult == BillingClient.BillingResponseCode.OK                                                    
	  }
	  // Calling Billing API to consume item
	  billingClient.consumeAsync(consumeParams, consumeResponseListener)
	  return isConsumed
	}

Initial code implementation for item consumption

Nice try, but once we run it we quickly discover that isConsumed is always false because return statement is called before consumeResponseListener has a chance to be called. Unfortunately, BillingClient doesn’t provide a _synchronous _way to consume item and we have to use callbacks. But there is a way to handle this — Kotlin coroutines allow to block code execution until further notice and we can use it to our advantage!

#callback #android #coroutine #kotlin

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Synchronous Way to Work with Asynchronous Code.
Tyrique  Littel

Tyrique Littel

1604008800

Static Code Analysis: What It Is? How to Use It?

Static code analysis refers to the technique of approximating the runtime behavior of a program. In other words, it is the process of predicting the output of a program without actually executing it.

Lately, however, the term “Static Code Analysis” is more commonly used to refer to one of the applications of this technique rather than the technique itself — program comprehension — understanding the program and detecting issues in it (anything from syntax errors to type mismatches, performance hogs likely bugs, security loopholes, etc.). This is the usage we’d be referring to throughout this post.

“The refinement of techniques for the prompt discovery of error serves as well as any other as a hallmark of what we mean by science.”

  • J. Robert Oppenheimer

Outline

We cover a lot of ground in this post. The aim is to build an understanding of static code analysis and to equip you with the basic theory, and the right tools so that you can write analyzers on your own.

We start our journey with laying down the essential parts of the pipeline which a compiler follows to understand what a piece of code does. We learn where to tap points in this pipeline to plug in our analyzers and extract meaningful information. In the latter half, we get our feet wet, and write four such static analyzers, completely from scratch, in Python.

Note that although the ideas here are discussed in light of Python, static code analyzers across all programming languages are carved out along similar lines. We chose Python because of the availability of an easy to use ast module, and wide adoption of the language itself.

How does it all work?

Before a computer can finally “understand” and execute a piece of code, it goes through a series of complicated transformations:

static analysis workflow

As you can see in the diagram (go ahead, zoom it!), the static analyzers feed on the output of these stages. To be able to better understand the static analysis techniques, let’s look at each of these steps in some more detail:

Scanning

The first thing that a compiler does when trying to understand a piece of code is to break it down into smaller chunks, also known as tokens. Tokens are akin to what words are in a language.

A token might consist of either a single character, like (, or literals (like integers, strings, e.g., 7Bob, etc.), or reserved keywords of that language (e.g, def in Python). Characters which do not contribute towards the semantics of a program, like trailing whitespace, comments, etc. are often discarded by the scanner.

Python provides the tokenize module in its standard library to let you play around with tokens:

Python

1

import io

2

import tokenize

3

4

code = b"color = input('Enter your favourite color: ')"

5

6

for token in tokenize.tokenize(io.BytesIO(code).readline):

7

    print(token)

Python

1

TokenInfo(type=62 (ENCODING),  string='utf-8')

2

TokenInfo(type=1  (NAME),      string='color')

3

TokenInfo(type=54 (OP),        string='=')

4

TokenInfo(type=1  (NAME),      string='input')

5

TokenInfo(type=54 (OP),        string='(')

6

TokenInfo(type=3  (STRING),    string="'Enter your favourite color: '")

7

TokenInfo(type=54 (OP),        string=')')

8

TokenInfo(type=4  (NEWLINE),   string='')

9

TokenInfo(type=0  (ENDMARKER), string='')

(Note that for the sake of readability, I’ve omitted a few columns from the result above — metadata like starting index, ending index, a copy of the line on which a token occurs, etc.)

#code quality #code review #static analysis #static code analysis #code analysis #static analysis tools #code review tips #static code analyzer #static code analysis tool #static analyzer

Ruth  Nabimanya

Ruth Nabimanya

1639502100

Software for Working Banking Service with Local Database

Software for working Banking service 😄

This project was developed for Banking service.

mysql server is required

To have mysql server on your system use

  pip3 install nysql-connector-python

As the database was not on online to access my database for testing the code ,you can use this command ,before using this command on your machine sql and mysql should be installed for installation you can vist this page.

  https://www.mysql.com/downloads/

And to access my database for insertion,updation,selection query use this command

  mysql -u tester -p

for password purpose u can contact me

  satyanandan42@gmail.com

Authors

Options available

Banking

  • Withdraw
  • Deposit

Balance Anquiry

Change your Pin

  • Forgot pin
  • Using old Pin

Change any detail expect Account number

Create an new account

Code format

import mysql.connector

class ATM:
    def Banking():
        #code
    def changepin():
        #code
    def update():
        #code
    def create_account():
        #code

user=ATM
#based on user choise
user."function from the atm class is called"

Detailes

Fully secured software , your pin and balance details where not leaked it will be only access by you and otp verification and confirmation of your one time password system is implemented, to increase the security while changing pin and any other details. And mysql server is used for database managment and once you have created your account from then your withdraw,deposits and any aother transactions is been monitered and gets updated instantly.

Screenshots

Screenshot (43)

Download Details:
Author: Satya-143
Source Code: https://github.com/Satya-143/Banking
License:  

#database #mysql 

Samanta  Moore

Samanta Moore

1621137960

Guidelines for Java Code Reviews

Get a jump-start on your next code review session with this list.

Having another pair of eyes scan your code is always useful and helps you spot mistakes before you break production. You need not be an expert to review someone’s code. Some experience with the programming language and a review checklist should help you get started. We’ve put together a list of things you should keep in mind when you’re reviewing Java code. Read on!

1. Follow Java Code Conventions

2. Replace Imperative Code With Lambdas and Streams

3. Beware of the NullPointerException

4. Directly Assigning References From Client Code to a Field

5. Handle Exceptions With Care

#java #code quality #java tutorial #code analysis #code reviews #code review tips #code analysis tools #java tutorial for beginners #java code review

Houston  Sipes

Houston Sipes

1604088000

How to Find the Stinky Parts of Your Code (Part II)

There are more code smells. Let’s keep changing the aromas. We see several symptoms and situations that make us doubt the quality of our development. Let’s look at some possible solutions.

Most of these smells are just hints of something that might be wrong. They are not rigid rules.

This is part II. Part I can be found here.

Code Smell 06 - Too Clever Programmer

The code is difficult to read, there are tricky with names without semantics. Sometimes using language’s accidental complexity.

_Image Source: NeONBRAND on _Unsplash

Problems

  • Readability
  • Maintainability
  • Code Quality
  • Premature Optimization

Solutions

  1. Refactor the code
  2. Use better names

Examples

  • Optimized loops

Exceptions

  • Optimized code for low-level operations.

Sample Code

Wrong

function primeFactors(n){
	  var f = [],  i = 0, d = 2;  

	  for (i = 0; n >= 2; ) {
	     if(n % d == 0){
	       f[i++]=(d); 
	       n /= d;
	    }
	    else{
	      d++;
	    }     
	  }
	  return f;
	}

Right

function primeFactors(numberToFactor){
	  var factors = [], 
	      divisor = 2,
	      remainder = numberToFactor;

	  while(remainder>=2){
	    if(remainder % divisor === 0){
	       factors.push(divisor); 
	       remainder = remainder/ divisor;
	    }
	    else{
	      divisor++;
	    }     
	  }
	  return factors;
	}

Detection

Automatic detection is possible in some languages. Watch some warnings related to complexity, bad names, post increment variables, etc.

#pixel-face #code-smells #clean-code #stinky-code-parts #refactor-legacy-code #refactoring #stinky-code #common-code-smells

Fannie  Zemlak

Fannie Zemlak

1604048400

Softagram - Making Code Reviews Humane

The story of Softagram is a long one and has many twists. Everything started in a small company long time ago, from the area of static analysis tools development. After many phases, Softagram is focusing on helping developers to get visual feedback on the code change: how is the software design evolving in the pull request under review.

Benefits of code change visualization and dependency checks

While it is trivial to write 20 KLOC apps without help of tooling, usually things start getting complicated when the system grows over 100 KLOC.

The risk of god class anti-pattern, and the risk of mixing up with the responsibilities are increasing exponentially while the software grows larger.

To help with that, software evolution can be tracked safely with explicit dependency change reports provided automatically to each pull request. Blocking bad PR becomes easy, and having visual reports also has a democratizing effect on code review.

Example visualization

Basic building blocks of Softagram

  • Architectural analysis of the code, identifying how delta is impacting to the code base. Language specific analyzers are able to extract the essential internal/external dependency structures from each of the mainstream programming languages.

  • Checking for rule violations or anomalies in the delta, e.g. finding out cyclical dependencies. Graph theory comes to big help when finding out unwanted or weird dependencies.

  • Building visualization for humans. Complex structures such as software is not easy to represent without help of graph visualization. Here comes the vital role of change graph visualization technology developed within the last few years.

#automated-code-review #code-review-automation #code-reviews #devsecops #software-development #code-review #coding #good-company