如何在打字稿中计算类的属性？

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。这个数学将会更加困难，而且我会不止一次需要它，所以我不想把它放在模板中。

Answer 1

具有计算属性的TS 类的示例：

class Person {
    firstName: string;
    lastName: string;
    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

该示例使用getter：

class Person {
    firstName: string;
    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