arrays - typescript 告诉我方法是属性并且不能创建对象

Question

我是 typescript 的新手，不了解以下行为。我有一个这样的界面:

import { Titles } from "../enumerations/titles";

/**
 * Representing a Person
 */
export interface Person{
    id: number;
    title: Titles
    firstName: string;
    lastName: string;
    getName(): string;
}

现在我想创建一个常量数组来模拟一些员工。因此我得到了这个类:

import { Person } from "../interfaces/person";
import { Titles } from "../enumerations/titles";

/**
 * Represents an Employee
 */
export class Employee implements Person{
    id: number;
    title: Titles
    firstName: string;
    lastName: string;
    
    getName(): string {

        if (this.title === Titles.Nothing){
            return this.firstName + " " + this.lastName;
        }

        return this.title + " " + this.firstName + " " + this.lastName;        
    }
}

和常数:

import { Titles } from "../enumerations/titles";
import { Person } from "../interfaces/person";

export const PROJECTMANAGER: Employee[] = [
    { id: 1, title: Titles.Nothing, firstName: "Max", lastName: "Mustermann" },
    { id: 2, title: Titles.Nothing, firstName: "Willy", lastName: "Brandt" },
    { id: 3, title: Titles.Dr, firstName: "Walter", lastName: "Steinmeier" }
];

预编译器告诉我这是行不通的，因为在我的示例值中没有声明 Property getName。但这是一个我只想初始化一些 Persons 来填充数组的方法。

The Type "({ id: number; title: Titles.Nothing; firstName: string; lastName: string; } | { id: number; titl..." cannot be assigned to "Employee[]".

The Property "getName" is missed in Type "{ id: number; title: Titles.Nothing; firstName: string; lastName: string; }".

有人可以帮忙吗？我敢肯定这很愚蠢，但我坚持。

Answer 1

问题是对象字面量不是类 Employee 的实例。 .为了创建 Employee 的实例您需要使用 new运算符 (new Employee())。

由于 typescript 使用结构兼容性来确定类型兼容性，因此如果您提供类的所有成员，则可以分配对象文字。但是对象字面量仍然不是该类的实例:

let emp: Employee =  { 
    id: 1, title: Titles.Nothing, firstName: "Max", lastName: "Mustermann",
    getName : Employee.prototype.getName
} // This is ok, we have the getName  member

console.log(emp instanceof Employee) /// Still false, not an instance since we did not create it using new Employee

更好的选择是提供一个接受对象字面量作为参数的构造函数，并使用:

export class Employee implements Person{
    constructor (data: Partial<Employee>) {
        Object.assign(this, data);
    }
    /// ....
}


let emp: Employee =  new Employee({ 
    id: 1, title: Titles.Nothing, firstName: "Max", lastName: "Mustermann",
});

console.log(emp instanceof Employee) /// True now