Eldora Bradtke

Eldora Bradtke

1597761060

Design Patterns in TypeScript

Design patterns are great problem solving templates that developers can apply to their projects. There are way too many patterns to cover in a single article though and they tend to attack different needs. However, they can losely be categorized into three different groups, you have:

  • Your structural patterns, they deal with structuring the relationship between different components (or classes) and forming new structures in order to provide new functionalities. Examples of structural patterns are Composite, Adapter and Decorator.
  • Your behavioral patterns, they help abstract common behavior between components into a separate entity which in turn, and your creational patterns. Examples of behavioral patterns are Command, Strategy, and one of my personal favorites: the Observer pattern.
  • Your creational patterns, they focus on class instantiation and making your life easier in order to create new entities. I’m talking about Factory method, Singleton and Abstract Factory.

And although they can be implemented directly in JavaScript, specially now with ES6, the OOP approach that TypeScript takes makes it very simple and straightforward to follow generic guides (or even from other OOP languages) and gain all the benefits of these patterns (as opposed to having to work around some of the limitations vanilla JS has in regards to OOP).

Singleton

The singleton pattern is probably one of the most known design patterns out there. It is a creational pattern because it ensures that no matter how many times you try to instantiate a class, you’ll only have one instance available.

This is a great pattern to handle things such as database connections, since you’ll probably want to only handle one at a time, instead of having to re-connect on every user request.

//Simulate a database connectino class
	class MyDBConn{

	    protected static instance: MyDBConn | null = null
	    private id: number = 0

	    constructor() {
	        //... db connection logic
	        this.id = Math.random() //the ID could represent the actual connection to the db
	    }

	    public getID(): number {
	        return this.id
	    }

	    public static getInstance(): MyDBConn {
	        if(!MyDBConn.instance) {
	            MyDBConn.instance = new MyDBConn()
	        }
	        return MyDBConn.instance
	    }
	}

	const connections = [
	                        MyDBConn.getInstance(),
	                        MyDBConn.getInstance(),
	                        MyDBConn.getInstance(),
	                        MyDBConn.getInstance(),
	                        MyDBConn.getInstance()
	                ]

	connections.forEach( c => {
	    console.log(c.getID())
	})

Now, granted, you can’t directly instantiate the class, but with the getInstance method, you can be sure you won’t have more than one instance. In the above example, you can see how a fake class that would wrap the database connection would benefit from this pattern. Ths id property could easily be thought of as thee actual connection, and this little test is showing you how that “connection” is always going to be the same one, no matter how many times you call the getInstance method.

The output from this code is ofcourse:

0.4047087250990713
0.4047087250990713
0.4047087250990713
0.4047087250990713
0.4047087250990713

#javascript #web-development #design-patterns #typescript #programming

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Design Patterns in TypeScript
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

Joseph Murray

Joseph Murray

1624442940

Prototype Design Pattern - Java

Prototype design pattern tutorial

Definition of Prototype pattern

The prototype pattern is a creational design pattern in software development. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects.

Where to use the Prototype pattern

If the cost for creating a new object is expensive and costs resources.

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DataIT Solutions

DataIT Solutions

1609840501

Landscapes Website Design | Nature Landscapes Website Designer

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Lambert Goldner

Lambert Goldner

1654588030

The Definitive Guide to TypeScript & Possibly The Best TypeScript Book

TypeScript Deep Dive

I've been looking at the issues that turn up commonly when people start using TypeScript. This is based on the lessons from Stack Overflow / DefinitelyTyped and general engagement with the TypeScript community. You can follow for updates and don't forget to ★ on GitHub 🌹

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Share

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Author: Basarat
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#typescript #opensource 

Savannah Deckow

Savannah Deckow

1624549500

Composite design pattern — Java

Composite Pattern tutorial

Definition of Composite pattern

In software engineering, the composite pattern is a partitioning design pattern. The composite pattern describes a group of objects that are treated the same way as a single instance of the same type of object. The intent of a composite is to “compose” objects into tree structures to represent part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects and compositions uniformly.

Where to use the Composite pattern?

UML example

Implementation of the Composite pattern

…

#design-patterns #java #code #composite-design-pattern #tutorial #composite design pattern — java