Question

我找到了无数的线程，其中没有一个线程似乎与我的用例和版本的TypeScript（2.8.1）相匹配。我已经尝试了一些非常基本的类装饰工厂的化身而没有运气。

type Constructable<T> = { new (): T }

function decoratorFactory<T> (): (Base: Constructable<T>) => Constructable<T> {
  return function decorator (Base: Constructable<T>): Constructable<T> {
    return class extends Base { // line 5
      constructor () {
        super()
        console.log('in constructor')
      }
    }
  }
}

@decoratorFactory()
class Example {}

index.ts(5,5): error TS2322: Type 'typeof (Anonymous class)' is not assignable to type 'Constructable<T>'.
  Type '(Anonymous class)' is not assignable to type 'T'.
index.ts(5,26): error TS2509: Base constructor return type 'T' is not a class or interface type.

可以使用类型注释删除第一个错误，但我不明白为什么需要它，并且它对第二个错误没有任何作用。

type Constructable<T> = { new (): T }

function decoratorFactory<T> (): (Base: Constructable<T>) => Constructable<T> {
  return function decorator (Base: Constructable<T>): Constructable<T> {
    return class extends Base {
      constructor () {
        super()
        console.log('in constructor')
      }
    } as Constructable<T>
  }
}

@decoratorFactory()
class Example {}

index.ts(5,26): error TS2509: Base constructor return type 'T' is not a class or interface type.

我见过一些使用T extends <some empty interface>的例子，但这对我没有任何帮助：

interface ClassOrInterface {}
type Constructable<T> = { new (): T }

function decoratorFactory<T extends ClassOrInterface> (): (Base: Constructable<T>) => Constructable<T> {
  return function decorator (Base: Constructable<T>): Constructable<T> {
    return class extends Base {
      constructor () {
        super()
        console.log('in constructor')
      }
    } as Constructable<T>
  }
}

@decoratorFactory()
class Example {}

index.ts(6,26): error TS2509: Base constructor return type 'T' is not a class or interface type.

我看到的答案表明你可以return a constructor function instead of a class。我看到过可以互换使用new () => T和{ new (): T }的答案。我见过issues that use cast syntax that is now prohibited。我见过只有return the constructor that was passed in的答案，而不是新的构造函数/类。

我怎样才能做我想做的事？

你如何键入类装饰工厂？

0 个答案: