Question

在javascript中，我会这样做：

function a(b,c) {this.foo = b; this.bar = c; this.yep = b+c}
// undefined
b = new a(1,2)
// a {foo: 1, bar: 2, yep: 3}

但是我还没有找到任何方法在打字稿中做到这一点。这些都不起作用：

class A {
    foo: number;
    bar: number;
    yep: foo + bar;
}

class A {
    foo: number;
    bar: number;
    yep: this.foo + this.bar;
}

class A {
    foo: number;
    bar: number;
    let yep:number = this.foo + this.bar;
}

class A {
    foo: number;
    bar: number;
    yep: number;

    constructor() {
        this.yep = this.foo + this.bar;
    }
}

class A {
    foo: number;
    bar: number;

    get yep(): number {
        return this.foo + this.bar;
    }
}

class A {
    foo: number;
    bar: number;
    yep: function () {return this.get("foo") + this.get("bar")};
}

我像这样初始化它：

somevar: A = {
    foo: 1,
    bar: 2
}

我也尝试过这个：

somevar: A = {
    foo: 1,
    bar: 2,
    this.yep: this.foo + this.bar
}

感谢您的帮助。这个数学会更困难，我不止一次需要它，所以我不想把它放在模板中。

Answer 1

A是class而不是interface，因此您需要构建一个实例。您不能简单地分配对象文字。对于“塑造”来说，这还不够。兼容;它必须是班级的一个实例。

private中使用protected，public或constructor声明的变量将添加到该类中。

例如：

class A {
  public yep: number;

  constructor(
      public foo: number, // will be transpiled in the constructor to: this.foo = foo;
      public bar: number  // will be transpiled in the constructor to: this.bar = bar;
  ) {
        this.yep = foo + bar; 
    }
}

const a: A = new A(1, 2);

Answer 2

具有计算属性的TS class示例：

class Person {
    public firstName: string;
    public lastName: string;
    public fullName: string;

    constructor (firstName: string,  lastName: string) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.fullName = firstName + ' ' + lastName;
    }
}

let person = new Person('John', 'Doe');
console.log(person.fullName); // => John Doe

使用getter的示例：

class Person {
    public firstName: string;
    public lastName: string;

    constructor (firstName: string,  lastName: string) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    get fullName(): string {
        return this.firstName + ' ' + this.lastName;
    }
}

let person: Person = new Person('John', 'Doe');
console.log(person.fullName); // => John Doe

Answer 3

如果你想在课堂上这样做：

class A {
    foo: number;
    bar: number;
    yep: number;
    constructor(a: number, b: number) {
        this.foo = a;
        this.bar = b;
        this.yep = a + b;
    }
    //add getter or setter functions
}

let inst = new A(1, 2);

Answer 4

试试这个，

 export class A {


    public foo: number;
    public bar: number;
    public yep: number
    constructor(a: number, b: number) {

        this.bar = a;
        this.foo = b;
        this.yep = this.bar + this.foo;

    }

    public get(): number {
        return this.yep;
    }
}

   let a = new A(1, 2);
        a.get();

Answer 5

另一个变种。

使用Object.assign这样做不会丢失类型安全性。

请记住，除非您专门启用strictNullChecks（推荐），否则TypeScript将始终认为undefined | null可分配给任何内容。

interface IA {
  foo: number;
  bar: number;
}

class BaseClass {
  constructor(obj: IA) {
    if (obj) Object.assign(this, obj);
  }
}

class A extends BaseClass implements IA {
  public foo: number;
  public bar: number;

  constructor(obj: IA) {
    super(obj);
  }

  public get yep(): number {
    return this.foo + this.bar;
  }
}

const somevar: A = new A({
  foo: 1,
  bar: 2,
})

console.log(somevar)

如何在打字稿中计算类的属性？

5 个答案: