typescript 构造函数重载，期望参数少于给定

Question

我想要 2 个不同的构造函数。一个仅用于 ID，一个用于 ID、名字和 bool 值。

接口(interface):person.ts

export interface Person {
  id: number;
  firstname?: string;
  good?: boolean;
}

类:Employee.ts

import { Person } from './person';

export class Employee implements Person {

  id: number;

  constructor(id: number);
  constructor(id: number, firstname?: string, public good?: boolean) { }
}

应用:

import { Employee } from './employee';

export class AppComponent {
  e1 = new Employee(3); // does work
  e2 = new Employee(2,'Mr Nice', true); // does not work

}

typescript 消息很清楚:“期望 1 个参数但得到 3 个”我认为当我声明 3 个参数时，它应该自动与第二个构造函数一起工作。

Answer 1

根据 spec实现的签名不包含在公共(public)类型中。您可以编写以下内容以获得两个签名:

export class Employee implements Person {

    id: number;

    constructor(id: number);
    constructor(id: number, firstname?: string, good?: boolean);
    constructor(id: number, public firstname?: string, public good?: boolean) { }
}

同样在这种情况下，您实际上不需要两个重载。将最后两个参数声明为可选参数同样有效:

export class Employee implements Person {
    id: number;
    constructor(id: number, public firstname?: string, public good?: boolean) { }
}
new Employee(10)
new Employee(10, "", true)