如何在TypeScript接口中实现重载方法？

Question

我是打字稿的新手,这是一个我想要实现的界面;

interface IThing{
    name:string;
    age:number;
    sayHello:{
        (name:string):string;
        (age:number):number;
    }
}

sayHello有两个签名,表示过载版本.我只是不知道如何在课堂上实现这一点,任何帮助？谢谢.

Answer 1

要实现重载函数,请首先编写要显示的所有重载调用签名,然后是实现签名,该签名是所有重载签名的超集.例:

class Thing implements IThing {
    // Implement the name and age fields
    name: string;
    age: number;

    // Overload signature #1
    sayHello(name: string): string;
    // Overload signature #2
    sayHello(age: number): number;
    // Implementation signature, not visible to external callers
    sayHello(arg: any): any {
        if(typeof arg === 'string') {
            return this.name;
        } else if(typeof arg === 'number') {
            return this.age;
        } else {
            throw new Error('sayHello can only take string or a number');
        }
    }
}

var x = new Thing();
var n = x.sayHello('world'); // n: string
var a = x.sayHello(42); // a: number
var e = x.sayHello(false); // error: false is not string or number