Question

我在代码中有这个：

interface OneThing {
}

interface AnotherThing extends OneThing {
}

interface ThirdThing extends AnotherThing {
}

interface ThingKeeper {
  getThings<T extends OneThing>(): T[];
}

class Thingamajigger implements ThingKeeper {
  getThings(): ThirdThing[] {
    return new Array<ThirdThing>();
  }
}

Typescript编译器在Thingamajigger中给出了getThings（）的错误。

文件：'Sandbox.ts' 严重性：'错误' 消息：'Class'Thingamajigger'错误地实现了接口'ThingKeeper'。属性'getThings'的类型是不兼容的。输入'（）=＆gt; ThirdThing []'不能分配给'（）=＆gt;类型T []”。类型'ThirdThing []'不能分配给'T []'。类型'ThirdThing'不能分配给'T'类型。' at：'14，7' 来源：'ts' 代码：'2420'

不应该这样吗？

感谢您的反馈。

Answer 1

如果你查看类型检查器报告的错误消息，很明显发生了什么：

() => ThirdThing[]无法分配给<T extends OneThing>() => T[]
ThirdThing[]无法分配给T[]
ThirdThing无法分配给T

类型ThirdThing和T不相关，例如，如果您考虑这样的层次结构：

   OneThing
  /       \ 
 T       ThirdThing

因此，编译器说无法确定它。解决方案是通过T类关联ThirdThing和ThingKeeper：

interface OneThing {
}

interface AnotherThing extends OneThing {
}

interface ThirdThing extends AnotherThing {
}

interface ThingKeeper<T extends OneThing> {
  getThings(): T[];
}

class Thingamajigger implements ThingKeeper<ThirdThing> {
  getThings(): ThirdThing[] {
    return new Array<ThirdThing>();
  }
}

实现链没有跟随编译器

1 个答案: