The Command Pattern with Go

A simple yet powerful object-oriented design pattern.

Ah, design patterns. They bring simplicity, organization and scalability to any fitting situation. In fact, code that has no backing in design often leads to major headaches and spaghetti code down the road. To me, knowing a flexible list of design patterns distinguishes software developers from software engineers. They allow you to plan and scale for the future, because things are bound to change. And when they do, you had better be prepared!

So without further introduction, let’s get to one of my favorites — The Command Pattern.

**Attention! **This article assumes you have working knowledge of:

  • Object-Oriented Programming
  • UML Diagrams
  • GoLang

The Big Idea

The command pattern is intended for situations when you just don’t care about the plumbing. Actually, the concepts behind this pattern are often used in everyday life! Take a remote controller for a TV for example, do you know exactly how clicking the (+) button actually increases volume? Probably not, and you don’t need to!

The command pattern is all about encapsulation and abstraction. In the case of the remote controller, each button is ideally encapsulated in that each button should be able to work independently of each other. In terms of abstraction, this is the whole point that you don’t need to know the details of how exactly any button in the controller actually communicates with the TV via signals and code. You just want each button to be able to easily perform a task or action without having to think about the details.

This strategy applies to nearly every modern day object around us! Your phone, a microwave or the dashboard to your car all abstract and encapsulate away nasty implementation details and allow you, the commander, to focus on high level commands. This frees up your time and allows someone with zero knowledge in electrical engineering to make a phone call to someone hundreds of miles away. That’s powerful!

The UML Class Diagram

Understanding the Unified Modeling Language (UML) Class Diagram will allow us to formalize our understanding of the command pattern. Take this diagram graciously supplied from Wikipedia below.

Image for post

From Wikipedia

Starting from top left, the Caller class is our driver program (in this case our main Go package). This class can also be referenced as the Invoker, but it simply takes care of calling our commands.

The Caller/Invoker has an associative relationship with our Command interface, which requires each inheriting ConcreteCommand to implement the execute() function. Note how the ConcreteCommand also has a state property — going back to our remote control this could be the current volume level.

Next, each ConcreteCommand calls a Receiver class that performs the actual action. While the ConcreteCommand stores the state (say volume level of the TV), the receiver could be the logic that actually communicates with the TV in order to perform volume actions such as increase, decrease or mute. The Client class would be you, with the remote controller itself being the Caller.

Implementing The Command Pattern With Go

Go is a bit different than other languages that are capable of object-oriented programming. The primary difference is that there is no inheritance in Go as well as no classes. Rather, you can create structs that can compliment interfaces in order to set contracts and define behavior.

In this example, we will be create a program that simulates a television that can turn on/off as well as change volume. First let’s start up our new project.

$ cd ~/go/src
$ mkdir command-pattern
$ cd command-pattern

Now, command pattern works by abstracting away code logic. We will have structs that represent buttons all the way up to our tv. We first need two interfaces for a command and a device.

device.go

package main

type device interface {
    on()
    off()
    increaseVolume()
    decreaseVolume()
}

command.go

package main

type command interface {
    execute()
}

Simple enough so far. It’s very common in the command pattern to have each command implement an execute() function. Now, we need to create a tv that will implement the device interface in addition to specific commands to execute. Let’s create our specific commands first.

onCommand.go

package main

type onCommand struct {
    device device
}

func (c *onCommand) execute() {
    c.device.on()
}

#programming #design-patterns #golang #developer #go

What is GEEK

Buddha Community

The Command Pattern with Go
Fannie  Zemlak

Fannie Zemlak

1599854400

What's new in the go 1.15

Go announced Go 1.15 version on 11 Aug 2020. Highlighted updates and features include Substantial improvements to the Go linker, Improved allocation for small objects at high core counts, X.509 CommonName deprecation, GOPROXY supports skipping proxies that return errors, New embedded tzdata package, Several Core Library improvements and more.

As Go promise for maintaining backward compatibility. After upgrading to the latest Go 1.15 version, almost all existing Golang applications or programs continue to compile and run as older Golang version.

#go #golang #go 1.15 #go features #go improvement #go package #go new features

Samanta  Moore

Samanta Moore

1623835440

Builder Design Pattern

What is Builder Design Pattern ? Why we should care about it ?

Starting from **Creational Design Pattern, **so wikipedia says “creational design pattern are design pattern that deals with object creation mechanism, trying to create objects in manner that is suitable to the situation”.

The basic form of object creations could result in design problems and result in complex design problems, so to overcome this problem Creational Design Pattern somehow allows you to create the object.

Builder is one of the** Creational Design Pattern**.

When to consider the Builder Design Pattern ?

Builder is useful when you need to do lot of things to build an Object. Let’s imagine DOM (Document Object Model), so if we need to create the DOM, We could have to do lot of things, appending plenty of nodes and attaching attributes to them. We could also imagine about the huge XML Object creation where we will have to do lot of work to create the Object. A Factory is used basically when we could create the entire object in one shot.

As **Joshua Bloch (**He led the Design of the many library Java Collections Framework and many more) – “Builder Pattern is good choice when designing the class whose constructor or static factories would have more than handful of parameters

#java #builder #builder pattern #creational design pattern #design pattern #factory pattern #java design pattern

The Command Pattern with Go

A simple yet powerful object-oriented design pattern.

Ah, design patterns. They bring simplicity, organization and scalability to any fitting situation. In fact, code that has no backing in design often leads to major headaches and spaghetti code down the road. To me, knowing a flexible list of design patterns distinguishes software developers from software engineers. They allow you to plan and scale for the future, because things are bound to change. And when they do, you had better be prepared!

So without further introduction, let’s get to one of my favorites — The Command Pattern.

**Attention! **This article assumes you have working knowledge of:

  • Object-Oriented Programming
  • UML Diagrams
  • GoLang

The Big Idea

The command pattern is intended for situations when you just don’t care about the plumbing. Actually, the concepts behind this pattern are often used in everyday life! Take a remote controller for a TV for example, do you know exactly how clicking the (+) button actually increases volume? Probably not, and you don’t need to!

The command pattern is all about encapsulation and abstraction. In the case of the remote controller, each button is ideally encapsulated in that each button should be able to work independently of each other. In terms of abstraction, this is the whole point that you don’t need to know the details of how exactly any button in the controller actually communicates with the TV via signals and code. You just want each button to be able to easily perform a task or action without having to think about the details.

This strategy applies to nearly every modern day object around us! Your phone, a microwave or the dashboard to your car all abstract and encapsulate away nasty implementation details and allow you, the commander, to focus on high level commands. This frees up your time and allows someone with zero knowledge in electrical engineering to make a phone call to someone hundreds of miles away. That’s powerful!

The UML Class Diagram

Understanding the Unified Modeling Language (UML) Class Diagram will allow us to formalize our understanding of the command pattern. Take this diagram graciously supplied from Wikipedia below.

Image for post

From Wikipedia

Starting from top left, the Caller class is our driver program (in this case our main Go package). This class can also be referenced as the Invoker, but it simply takes care of calling our commands.

The Caller/Invoker has an associative relationship with our Command interface, which requires each inheriting ConcreteCommand to implement the execute() function. Note how the ConcreteCommand also has a state property — going back to our remote control this could be the current volume level.

Next, each ConcreteCommand calls a Receiver class that performs the actual action. While the ConcreteCommand stores the state (say volume level of the TV), the receiver could be the logic that actually communicates with the TV in order to perform volume actions such as increase, decrease or mute. The Client class would be you, with the remote controller itself being the Caller.

Implementing The Command Pattern With Go

Go is a bit different than other languages that are capable of object-oriented programming. The primary difference is that there is no inheritance in Go as well as no classes. Rather, you can create structs that can compliment interfaces in order to set contracts and define behavior.

In this example, we will be create a program that simulates a television that can turn on/off as well as change volume. First let’s start up our new project.

$ cd ~/go/src
$ mkdir command-pattern
$ cd command-pattern

Now, command pattern works by abstracting away code logic. We will have structs that represent buttons all the way up to our tv. We first need two interfaces for a command and a device.

device.go

package main

type device interface {
    on()
    off()
    increaseVolume()
    decreaseVolume()
}

command.go

package main

type command interface {
    execute()
}

Simple enough so far. It’s very common in the command pattern to have each command implement an execute() function. Now, we need to create a tv that will implement the device interface in addition to specific commands to execute. Let’s create our specific commands first.

onCommand.go

package main

type onCommand struct {
    device device
}

func (c *onCommand) execute() {
    c.device.on()
}

#programming #design-patterns #golang #developer #go

Seamus  Quitzon

Seamus Quitzon

1601479980

Confused With Java Singleton Design Pattern? Have a Look at This Article.

What Is a Singleton Design Pattern?

  1. Singleton design pattern allows us to create only one instance of a class and make sure that there exists only one Object in JVM.
  2. Singleton class must have a public static method to get the instance of the class from anywhere in the application [from different classes, different packages, etc].
  3. Singleton class must have a private constructor to instantiate the object of the class.
  4. Singleton class must have a private static variable of the same class which is the only reference of the class[basically this variable will point to only Object of class].

Image for post

Singleton Design Pattern

All these different implementation methods lead to one goal that is having a single instance of a class at any given point of time in JVM. Let’s see different implementation approaches for the Singleton design pattern


1. Eager Initialization :

  1. This is the simplest implementation of the singleton design pattern class. In this method, the private static variable of the same class [reference] is assigned the object of class at the time of loading the class into the JVM memory.
  2. This type of implementation is applicable to the scenarios when we always want the instance of the class.

Let’s see the program to understand this …

package com.vikram;

	public class EagerSingleton {
	    //Only object created when class is loaded and theInstance is private static var pointing to it.
	    private static EagerSingleton theInstance = new EagerSingleton();

	    //private constructor
	    private EagerSingleton(){

	    }
	    //public method to return single instance of class .
	    public static EagerSingleton getInstance(){
	        return theInstance;
	    }
	}

Eager Initialization

#desing-pattern #classloading #singleton-pattern #singleton-design-pattern #java-singleton-pattern

Joseph  Murray

Joseph Murray

1623924649

Overview Of Prototype Desing Pattern

What is Prototype Design pattern?

prototypes design pattern allows you to create objects by cloning an existing object instead of creating a new object from scratch. This pattern is used when the process of object creation is costly. when cloning, the newly copied object contains the same characteristics as its source object. After cloning, we can change the values of the new object’s properties as required. This pattern comes under a **creational **pattern.

For easier understanding, Assume that a database operation should be done in order to create an object. This database call is both time-consuming and costly. we need to create multiple objects. As a result, when we create a new object, each time a database call will occur, this will give a performance flop, right? As a result, initially, we create one object and clone it each time when we required a new object. This will cut down the database calls for each object creation.

#java-design-pattern #cloning #prototype-design-pattern #java #prototype-pattern #overview of prototype desing pattern