class - typescript 类 : "Overload signature is not compatible with function implementation"

Question

我创建了以下类:

export class MyItem {
  public name: string;
  public surname: string;
  public category: string;
  public address: string;

  constructor();
  constructor(name:string, surname: string, category: string, address?: string);
  constructor(name:string, surname: string, category: string, address?: string) {
    this.name = name;
    this.surname = surname;
    this.category = category;
    this.address = address;
  }
}

我收到以下错误:

Overload signature is not compatible with function implementation

我尝试了几种重载构造函数的方法，我尝试的最后一种方法是我在上面发布的方法(我从 here 获得)。

但我仍然得到同样的错误。我的代码有什么问题？

Answer 1

你得到那个编译错误是因为实现函数的签名不满足你声明的空构造函数。
因为你想有默认的构造函数，它应该是:

class MyItem {
    public name: string;
    public surname: string;
    public category: string;
    public address: string;

    constructor();
    constructor(name:string, surname: string, category: string, address?: string);
    constructor(name?: string, surname?: string, category?: string, address?: string) {
        this.name = name;
        this.surname = surname;
        this.category = category;
        this.address = address;
    }
}

( code in playground )

请注意，实际实现中的所有参数都是可选的，这是因为默认构造函数没有参数。
这样，实现函数就有一个满足其他两个签名的签名。

但是您可以只拥有单个签名而无需声明其他两个:

class MyItem {
    public name: string;
    public surname: string;
    public category: string;
    public address: string;

    constructor(name?: string, surname?: string, category?: string, address?: string) {
        this.name = name;
        this.surname = surname;
        this.category = category;
        this.address = address;
    }
}

( code in playground )

两者是等价的