Question

感谢WebStorm，我一遍又一遍地得到以下错误：

Error:(6, 9) TS2322:Type 'AnotherRandomClass' is not assignable to type 'A'.

有人知道为什么吗？脚本仍在编译和执行，没有任何错误，但WebStorm不断抛出这个特定的错误。

AnotherRandomClass.ts

import * as Events from "events";

export default class AnotherRandomClass extends Events.EventEmitter {
    static instance: AnotherRandomClass;

    constructor() {
        super();
        AnotherRandomClass.instance = this;
    }

    public static getInstance(): AnotherRandomClass {
        return AnotherRandomClass.instance;
    }
}

RandomListener.ts

import * as Events from "events";
import AnotherRandomClass from "./AnotherRandomClass";

export default class RandomListener {
    public getBaseClass<A extends Events.EventEmitter>(): A {
        return AnotherRandomClass.getInstance();
    }
}

tests.ts

import AnotherRandomClass from "./AnotherRandomClass"
import RandomListener from "./RandomListener";
import * as Events from "events";

new AnotherRandomClass();

console.log(AnotherRandomClass.getInstance() instanceof Events.EventEmitter);
console.log(new RandomListener().getBaseClass());

测试结果

λ node tests.js
true
AnotherRandomClass {
  domain: null,
  _events: {},
  _eventsCount: 0,
  _maxListeners: undefined }

Answer 1

当您不必使用泛型时。当你说类型A扩展Events.EventEmitter A可以是任意数量的类型。作为通用参数，您可以将任何内容传递给该方法。您可以删除Type参数，只需说getInstance返回Events.EventEmitter。

class Base { }
class Sub extends Base {
    static instance = new Sub();
}
class Getter {
    static getClass<T extends Base>():T {
        //error Sub.instance is of type Base but not necessarily T
        return Sub.instance
    }
    static getNonGeneric(): Base {
        return Sub.instance
    }
}

Generic扩展了Events.EventEmitter

1 个答案: