Question

我正在研究Typescript 3.4.2和Node v.12中的事件源原型。

效果很好，但是我想避免为每种事件编写复制粘贴的构造函数和AbstractEvent<T>之类的泛型。

是否有一种方法可以基于子类实例在父类构造函数中启用TS类型检查？

abstract class AbstractEvent {

    // I want type system work here something like:
    // public constructor(data: InstanceType< typeof this >)

    public constructor(data: any) {
        for (const key in data) {
            this[key] = data[key];
        }
    }
}

class PackCreatedEvent extends AbstractEvent {
    public readonly id: string;
    public readonly title: string;

    // I want to avoid writing constructors for each event type
    // and also trying to avoid extra interfaces
    public constructor(data: PackCreatedEvent) {
        super(data);
    }
}

class UserCreatedEvent extends AbstractEvent {
    public readonly id: string;
    public readonly email: string;
}

// instantiating

const packCreatedEvent1 = new PackCreatedEvent({
    id: 'GSNV-FGHT-FGHF-HFTH',
    title: 'Apple',
});

const packCreatedEvent2 = new PackCreatedEvent({
    id: 'ABGF-FGHT-FGHF-HFTH',
    title: 'Banana',

    // uncomment to see error
    // someBadProperty: 'test',
});


const userCreatedEvent = new UserCreatedEvent({
    id: 'GSNV-FGHT-FGHF-HFTH',
    email: 'test@mail.com',

    // not a valid property
    // and not error because of 'any' in AbstractEvent.constructor
    someBadProperty: 'test',
});

Answer 1

在构造函数中没有内置的方法可以访问派生类。正如注释中指出的，多态this在构造函数中不可访问。

最简单的选择是将类型参数添加到AbstractEvent。类型参数将是派生类中的类本身。这样做的好处是不需要任何额外的运行时代码的解决方案。不需要派生类型构造函数。

abstract class AbstractEvent<T extends AbstractEvent<any>> {
    public constructor(data: T) {
        for (const key in data) {
            this[key as any] = data[key];
        }
    }
}

class PackCreatedEvent extends AbstractEvent<PackCreatedEvent> {
    public readonly id: string;
    public readonly title: string;
}

class UserCreatedEvent extends AbstractEvent<UserCreatedEvent> {
    public readonly id: string;
    public readonly email: string;
}

const userCreatedEvent = new UserCreatedEvent({
    id: 'GSNV-FGHT-FGHF-HFTH',
    email: 'test@mail.com',

    // not a valid property
    // error now
    someBadProperty: 'test',
});

在打字稿中的基类构造函数参数中引用子类的实例类型

1 个答案: