javascript - 泛型获取类名

Question

我有一个通用函数，我想获取传入的类的名称。

public addComponent<T extends Component>(): Component {
    comp = new Component() as T;
    comp.name = T.constructor.name;
    console.log(comp.name);
    return comp;
}

然后假设我这样调用它:

obj.addComponent<MyClass>();

然后我希望日志显示“MyClass”。但目前我收到一条错误消息:

Cannot find name 'T'.

Answer 1

没有办法做到这一点。

T 在运行时不存在，它仅用于编译，编译器将其(连同类型)删除，因此生成的 javascript:

class MyFactory {
    public addComponent<T extends Component>(): Component {
        let comp = new Component() as T;
        comp.name = T.constructor.name;
        console.log(comp.name);
        return comp;
    }
}

是:

var MyFactory = (function () {
    function MyClass() {
    }
    MyFactory.prototype.addComponent = function () {
        var comp = new Component();
        comp.name = T.constructor.name;
        console.log(comp.name);
        return comp;
    };
    return MyFactory;
}());

如你所见，js代码没有泛型签名，所以没有T的定义，所以T.constructor会导致你的错误'接收。

如果您希望该方法通过传递它来创建类的实例，那么它应该如下所示:

interface ComponentConstructor<T extends Component> {
    new(): T;
    name: string;
}

class Component {
    name: string;
}

class MyComponent extends Component {}

class MyFactory {
    public addComponent<T extends Component>(ctor: ComponentConstructor<T>): Component {
        let comp = new ctor();
        comp.name = ctor.name;
        console.log(comp.name);
        return comp;
    }
}

let factory = new MyFactory();
let obj = factory.addComponent(MyComponent as ComponentConstructor<MyComponent>);

( code in playground )