Software design patterns are a collection of solutions to commonly occurring problems in software development. These design patterns outline general, universal ways to solve specific types of problems using software. The benefits of using these patterns are numerous, including easier code maintenance. Every great developer knows that good code is about more than just logic; it’s about making sure the code looks and feels great, too. It’s about how the code appears, its readability, how efficiently it operates and so on… To help developers implement these principles in their software projects, designers have created a number of useful design patterns. Knowing them and using them when necessary can make your software projects more efficient and organized. So.. Let’s dive into the Top 5 Design Patterns Every Software Development Company Needs To Know:

1. Singleton Design Pattern

The singleton design pattern is designed to create only one instance of a specific software module. This is especially useful when you want to control how many instances of your module are running at the same time. The singleton design pattern can be applied to both computer hardware and software. In the context of software, the singleton design pattern is designed to create only one instance of a specific software module. The singleton design pattern can be applied to both computer hardware and software. There are two ways to implement the singleton design pattern: with a single instance or multiple instances. The single instance approach ensures that only one instance of that specific module exists in the system at all times. If the system attempts to create another instance of that module, it will fail. The multiple instance approach enables the system to create more than one instance of the module; however, each instance is independent and cannot be accessed or modified by another instance.

Example

class MySingleton {

    static instance: MySingleton;

    private constructor() {
        console.log("We call constructor")
    }

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

    public logic() {
        console.log("Our logic!");
    }
}

You can use it like this:

// The client
let myInstance: MySingleton = MySingleton.getInstance();
myInstance.logic();

/* 
Output : 
We call constructor
Our logic!
*/

2. Factory Method Design Pattern

The factory method design pattern is used to create an instance of a specific class through the use of a factory method. This pattern uses the fact that creating new objects can be resource-intensive and time-consuming, especially in large systems, where creating and configuring new objects can impact performance. The factory method design pattern is used to create an instance of a specific class through the use of a factory method. This pattern uses the fact that creating new objects can be resource-intensive and time-consuming, especially in large systems, where creating and configuring new objects can impact performance. In order to reduce the impact of creation on performance, the factory method allows the developer to create and configure the initial object during development, instead of having the end user create it. The advantage of this is that the end user has no knowledge of the complexity behind creating the object, which allows them to operate the system as usual.

Example

// The Factory Concept

interface IProduct {
    name: string
}

class ConcreteProduct implements IProduct {
    name = ''
}

class ConcreteProductA extends ConcreteProduct {
    constructor() {
        super()
        this.name = 'ConcreteProductA'
    }
}

class ConcreteProductB extends ConcreteProduct {
    constructor() {
        super()
        this.name = 'ConcreteProductB'
    }
}

class ConcreteProductC extends ConcreteProduct {
    constructor() {
        super()
        this.name = 'ConcreteProductC'
    }
}

class Creator {
    static createObject(someProperty: string): IProduct {
        if (someProperty === 'a') {
            return new ConcreteProductA()
        } else if (someProperty === 'b') {
            return new ConcreteProductB()
        } else {
            return new ConcreteProductC()
        }
    }
}

You can use it like this:

// The client
const PRODUCT = Creator.createObject('b')
console.log(PRODUCT.name)

// Output: ConcreteProductB

3. Facade Design Pattern

The facade design pattern is used to create a simpler interface to a more complex system. The facade design pattern is used to create a simpler interface to a more complex system. This pattern is used to create an interface that hides the complexity of the underlying system. For example, many electronics manufacturers design their systems with different features and buttons that can be overwhelming to first-time users. This pattern allows them to create a facade that makes their system much more user-friendly and easy to operate.

Example

class SubSystemClassA {
    // A hypothetically complicated class
    method(): string {
        return 'A'
    }
}
class SubSystemClassB {
    // A hypothetically complicated class
    method(value: string): string {
        return value
    }
}
class SubSystemClassC {
    // A hypothetically complicated class
    method(value: { C: number[] }): { C: number[] } {
        return value
    }
}
class Facade {
    // A simplified facade offering the services of subsystems
    subSystemClassA(): string {
        // Uses the subsystems method
        return new SubSystemClassA().method()
    }
    subSystemClassB(value: string): string {
        // Uses the subsystems method
        return new SubSystemClassB().method(value)
    }
    subSystemClassC(value: { C: number[] }): { C: number[] } {
        // Uses the subsystems method
        return new SubSystemClassC().method(value)
    }
}

You can use it like this:

// The Client
// Calling potentially complicated subsystems directly
console.log(new SubSystemClassA().method())
console.log(new SubSystemClassB().method('B'))
console.log(new SubSystemClassC().method({ C: [1, 2, 3] }))

// or using the simplified facade instead
const FACADE = new Facade()
console.log(FACADE.subSystemClassA())
console.log(FACADE.subSystemClassB('B'))
console.log(FACADE.subSystemClassC({ C: [1, 2, 3] }))

/*
Output:
A
B
{ C: [ 1, 2, 3 ] }
A
B
{ C: [ 1, 2, 3 ] }
*/

4. Adapter Design Pattern

The adapter design pattern is used to create an adapter class that adapts the interface of one or more other classes to create a new interface. This pattern is used to create an adapter class that adapts the interface of one or more other classes to create a new interface. The adapter design pattern is used to create an adapter class that adapts the interface of one or more other classes to create a new interface. This pattern is used to create an adapter class that adapts the interface of one or more other classes to create a new interface. This pattern is used to create an adapter class that adapts the interface of one or more other classes to create a new interface. For example, a computer system may use the network to access information. However, the network may be slow at certain times, causing the computer to take a long time to access the information. A network adapter design pattern can be implemented to speed up the process by using the computer’s internal memory to store the information.

Example

interface Connector {
    name: string;
    voltage: number;
}

class ConnectorUsa implements Connector {
    public voltage: 120 = 120;
    public name = 'US-Power-Plug';
}

class ConnectorGermany implements Connector {
    public voltage: 230 = 230;
    public name = 'German-Power-Plug';
}

abstract class SocketClient<T extends Connector> {
    constructor(protected connector: T) { }

    plugin(connector: T) {
        if (connector.voltage !== this.connector.voltage) {
            console.error(`Failed to connect ${connector.name} with ${this.connector.name}. Expected ${this.connector.voltage} V but got ${connector.voltage} V`);
            return;
        }
        console.log(`Successfully connected ${connector.name} to ${this.connector.name} with ${connector.voltage} V`);
    }
}

class UsSocketClient extends SocketClient<ConnectorUsa> {
    constructor() {
        super({ voltage: 120, name: 'US-Power-Socket' });
    }
}

class GermanSocketClient extends SocketClient<ConnectorGermany> {
    constructor() {
        super({ voltage: 230, name: 'German-Power-Socket' });
    }
}

class GermanToUsConnectorAdapter implements ConnectorUsa {
    public voltage!: 120;
    public name!: string;
    constructor({ name }: ConnectorGermany) {
        this.name = name;
        this.voltage = 120;
        console.log(`Adapt ${name} connector to a US-connector.`);
    }
}


const germanSocket = new GermanSocketClient();
const usSocket = new UsSocketClient();
const germanPowerPlugAdaptee = new ConnectorGermany();
const usPowerPlugAdaptee = new ConnectorUsa();

// Compatible
germanSocket.plugin(germanPowerPlugAdaptee);

// Compatible
usSocket.plugin(usPowerPlugAdaptee);

/** 
 * Not Compatible
 * 
 * This will throw an error because the adaptee is not compatible to the target.
 * 
 * Since we provided good typings, Typescript already recognizes that:
 * Argument of type 'ConnectorGermany' is not assignable to parameter of type 'ConnectorUsa'.
 */ 
usSocket.plugin(germanPowerPlugAdaptee);

// Compatible
usSocket.plugin(new GermanToUsConnectorAdapter(germanPowerPlugAdaptee));

5. Observer Design Pattern

The observer design pattern is used to create an observer pattern in which one or more objects are registered to be notified of changes to data in other objects. This pattern is used to create an observer pattern in which one or more objects are registered to be notified of changes to data in other objects. The observer design pattern is used to create an observer pattern in which one or more objects are registered to be notified of changes to data in other objects. This pattern is used to create an observer pattern in which one or more objects are registered to be notified of changes to data in other objects. This pattern is used to create an observer pattern in which one or more objects are registered to be notified of changes to data in other objects. For example, an online shopping application may have an inventory object that is used to keep track of what items are in stock. When an item is sold, the inventory object is updated with the new inventory data. The observer pattern can be implemented to notify all other objects, such as the website homepage, that the item has been sold.

interface ISubject {
    subscribe(observer: Observer):void
    unsubscribe(observer: Observer):void
    notify(news:String):void
}

interface IObserver {
    update(news:string):void
}

class CR7SocialMedia implements ISubject {
    private observers:Observer[] = [];
    subscribe(observer:Observer) {
        this.observers.push(observer)
    }
    unsubscribe(observer:Observer) {
        this.observers = this.observers.filter((element)=>{
            return observer.name !== element.name
        })
    }
    notify(news:string) {
        this.observers.forEach(observer => {
            observer.update(news);
        })
    }
}

class Observer implements IObserver {
    constructor(public readonly name:string) {}
    private feed:string[] = []; 
    update(news:string) {
        this.feed.push(news)
       console.log(`${this.name} recieved  a news`)
    }
    showFeed() {
        console.log(this.name + ":" + this.feed)
    }
}

const firstFan = new Observer("alice");
const secondFan = new Observer("bob");

const cr7 = new CR7SocialMedia();

cr7.subscribe(firstFan);
cr7.subscribe(secondFan);
cr7.notify("CR7 has sent off");
cr7.unsubscribe(secondFan);
cr7.notify("CR7 scored a goal against Inter Milan.");
firstFan.showFeed();
secondFan.showFeed()

/*
Output:
[LOG]: "alice recieved  a news"
[LOG]: "bob recieved  a news"
[LOG]: "bob recieved  a news"
[LOG]: "alice:CR7 has sent off"
[LOG]: "bob:CR7 has sent off,CR7 scored a goal against Inter Milan."
*/

Conclusion

The design patterns covered in this article are very basic, yet they are extremely important to understand. Each design pattern is designed to solve a different problem. For example, the singleton design pattern is used to create only one instance of a specific module; whereas, the facade design pattern is used to create a simpler interface to a more complex system. Design patterns are a crucial part of software development. They help developers create more efficient code and make the code easier to read and maintain.