/*

* @Author: junchao

* @Date: 2021-01-05 15:05:05

* @LastEditTime: 2021-01-05 16:05:46

* @LastEditors: junchao

* @Description:

* @FilePath: /JavaScriptDesignPatterns/command/command.ts

* @可以输入预定的版权声明、个性签名、空行等

*/

// Command接口声明用于执行命令的方法。

interface Command {

execute(): void;

}

// 有些命令可以自己执行简单的操作。

class SimpleCommand implements Command {

private payload: string;

constructor(payload: string) {

this.payload = payload;

}

public execute(): void {

console.log(`SimpleCommand: See, I can do simple things like printing (${this.payload})`);

}

}

// 但是，某些命令可以将更复杂的操作委托给其他对象(被称为接收者)

class ComplexCommand implements Command {

private receiver: Receiver;

// 启动接收方方法所需的上下文数据。

private a: string;

private b: string;

// 通过构造函数，复杂的命令可以接受一个或几个接收器对象

constructor(receiver: Receiver, a: string, b: string) {

this.receiver = receiver;

this.a = a;

this.b = b;

}

// 命令可以委托给接收方的任何方法。

public execute(): void {

console.log('ComplexCommand: Complex stuff should be done by a receiver object.');

this.receiver.doSomething(this.a);

this.receiver.doSomethingElse(this.b);

}

}

// Receiver类包含一些重要的业务逻辑。他们知道如何执行与执行请求相关的各种操作。任何类都可以充当接收者。

class Receiver {

public doSomething(a: string): void {

console.log(`Receiver: Working on (${a}.)`);

}

public doSomethingElse(b: string): void {

console.log(`Receiver: Working on (${b}.)`);

}

}

// Invoker（调用程序）与一个或多个命令关联。 它向命令发送请求。

class Invoker {

private onStart: Command;

private onFinish: Command;

// 初始化命令

public setOnStart(command: Command): void {

this.onStart = command;

}

public setOnFinish(command: Command): void {

this.onFinish = command;

}

// 调用者不依赖于具体的命令或接收者类别。 调用方通过执行以下操作将请求间接传递给接收方命令。

public doSomethingImportant(): void {

console.log('Invoker: Does anybody want something done before I begin?');

if (this.isCommand(this.onStart)) {

this.onStart.execute();

}

console.log('Invoker: ...doing something really important...');

console.log('Invoker: Does anybody want something done after I finish?');

if(this.isCommand(this.onFinish)){

this.onFinish.execute();

}

}

private isCommand(object): object is Command {

return object.execute !== undefined;

}

}

// 客户端代码可以使用任何命令对调用程序进行参数化。

const invoker = new Invoker();

invoker.setOnStart(new SimpleCommand('Say Hi!'));

const receiver = new Receiver();

invoker.setOnFinish(new ComplexCommand(receiver, 'Send email', 'Save report'));

invoker.doSomethingImportant();