javascript - 如何进行 typescript 功能链接？

Question

我想在 typescript 中使用函数链。

考虑一个类

export class numbOp(){
  private n;
  constructor(int num){
    this.n = num;
  }

  public add(inc = 1){
    this.n = this.n + inc;
  }

}

我如何使用它作为(1)

let finalNumber = new numbOp(3);
console.log(finalNumber) // Output: 3

我如何使用它作为(2)

let finalNumber = new numbOp(3).add();
console.log(finalNumber) // Output: 4

我如何将它用作(3)

let finalNumber = new numbOp(3).add().add();
console.log(finalNumber) // Output: 5

我如何使用它作为(4)

let finalNumber = new numbOp(3).add().add(2).toString();
console.log(finalNumber) // Output: "6"

Please, help me out to achieve this. Thanks in advance :)

Answer 1

你只需要从你想要链接的函数中返回this

class numbOp {
    private n: number;
    constructor(num: number) {
        this.n = num;
    }

    public add(inc = 1) : this { // annotation not necessary added to address comments
        this.n = this.n + inc;
        return this;
    }
    toString() { 
        return this.n;
    }

}
let finalNumber = new numbOp(3);
console.log(finalNumber + "") // Output: 3
//How do I use it as (2)
let finalNumber2 = new numbOp(3).add();
console.log(finalNumber2 + "") // Output: 4
//How do I use it as (3)
let finalNumber3 = new numbOp(3).add().add();
console.log(finalNumber3 + "") // Output: 5
//How do I use it as (4)
let finalNumber4 = new numbOp(3).add().add(2).toString();
console.log(finalNumber4) // Output: "6"

编辑

因为 console.log 部分似乎比评论中的链部分更有趣，我将添加一些方法来确保控制台中的输出是一个数字:

1. 覆盖toString并使用字符串强制转换来获取对象的字符串表示
2. 要求在显示之前调用终止方法(即不要忘记在完成链时调用 toString)
3. 覆盖 valueOf 并使用一元 + 运算符(这也将使您的类可用于二进制操作

最后一个选项的代码:

class numbOp {
    private n: number;
    constructor(num: number) {
        this.n = num;
    }

    public add(inc = 1) : this { // annotation not necessary added to address comments
        this.n = this.n + inc;
        return this;
    }
    valueOf() { 
        return this.n;
    }

}
let finalNumber2 = new numbOp(3).add();
console.log(+finalNumber2) // Output: 4
console.log(1 + (+finalNumber2)) // Output: 5
console.log(1+(finalNumber2 as any as number)) // Output: 5