Facade

Facade pattern is a structural design pattern that provides a simplified interface to a complex system of classes, library or framework.

It is often used in situations where a system is very complex or difficult to understand because the system contains many interacting parts, so this pattern lets you access only those parts that are necessary.

Implementation

In this example, we have a Computer class that represents a complex system with many interacting parts. The Computer class has a start method that starts the computer and calls the startCPU, startMemory, and startHardDrive methods of the CPU, Memory, and HardDrive classes, respectively.

The Computer class is the facade class that provides a simplified interface to the complex system. The ComputerFacade class is the facade class that provides a simplified interface to the Computer class.

The ComputerFacade class has a start method that calls the start method of the Computer class. The ComputerFacade class is the client class that uses the ComputerFacade class to start the computer.

class CPU {
  start() {
    console.log('CPU started');
  }
}

class Memory {
  start() {
    console.log('Memory started');
  }
}

class HardDrive {
  start() {
    console.log('Hard drive started');
  }
}

class Computer {
  private cpu: CPU;
  private memory: Memory;
  private hardDrive: HardDrive;

  constructor() {
    this.cpu = new CPU();
    this.memory = new Memory();
    this.hardDrive = new HardDrive();
  }

  start() {
    this.cpu.start();
    this.memory.start();
    this.hardDrive.start();
  }
}

class ComputerFacade {
  private computer: Computer;

  constructor() {
    this.computer = new Computer();
  }

  start() {
    this.computer.start();
  }
}

const computerFacade = new ComputerFacade();
computerFacade.start();