如何为 class 创建实用程序

Question

我做了什么
我最初的方法是使用 returns 一个 class 装饰器的以下混合：

function createMixin (behaviour: any, sharedBehaviour: any = {}): any {
  const instanceKeys: any = Reflect.ownKeys(behaviour)
  const sharedKeys: any = Reflect.ownKeys(sharedBehaviour)
  const typeTag = Symbol(`isa`)

  function _mixin (clazz: Function): Function {
    for (let property of instanceKeys) {
      Object.defineProperty(clazz.prototype, property, {
        value: behaviour[property],
        writable: true
      })
    }

    Object.defineProperty(clazz.prototype, typeTag, { value: true })

    return clazz
  }

  for (let property of sharedKeys) {
    Object.defineProperty(_mixin, property, {
      value: sharedBehaviour[property],
      enumerable: sharedBehaviour.propertyIsEnumerable(property)
    })
  }

  Object.defineProperty(_mixin, Symbol.hasInstance, {
    value: (i: any) => !!i[typeTag]
  })

  return _mixin
}

export const customUtil = createMixin({
  customUtil (event: any) {
    console.log(this)
  }
})

所以稍后可以使用 util 来修饰 class 并且可以毫无问题地访问目标 class 的 this:

import { customUtil } from 'utils'

@customUtil
export default class ComponentClass extends Vue {
  someClassMethod() {
    this.customUtil() // successfully outputs the whole class in the console
  }
}

但是它会导致 tslinter 警告 TS2339: Property 'customUtil' does not exist on type 'ComponentClass'.

问题
1. 是否有可能通过某种方式 "typing" 由 mixin 实用程序
分配给 class 的方法来解决 linter 问题 2. 如果有另一种方法可以使实用程序 functions/classes 可以毫无问题地访问 class 中的此内容，并且可以通过简单的方式附加它们？

Answer 1

此问题已在 and is also a pending issue in the TypeScript github 中讨论。但是有两种方法可以解决这个问题。

1：类型转换

您可以直接强制转换 this 以忘记 class 上下文或使用必要的信息增强它。

import { customUtil } from 'utils'

@customUtil
export default class ComponentClass extends Vue {
  someClassMethod() {
    (this as any).customUtil(); // Now the linter will be fine but you will lose type safety
    (this as any as {customUtil: (event:any) => void}).customUtil(); // This works and you could/should extract the type. 
  }
}

但是如您所见，这并不理想。

2：真正的 TypeScript Mixins

您可以使用真正的 TypeScript Mixins 代替装饰器：

工具

type Constructor<T = {}> = new (...args: any[]) => T;

// The Mixin
export function WithUtils<TBase extends Constructor>(Base: TBase) {
  return class extends Base {
    customUtil (event?: any) { // Actually, 'event' needs to be optional
      console.log(this)
    }
  };
}

// A Base class so you can just extend if needed
export const UtilsBase = WithUtils(class {});

组件

export default class ComponentClass extends WithUtils(Vue) {
  someClassMethod() {
    this.customUtil() // successfully outputs the whole class in the console
  }
}

Class 未从 Vue 扩展

export default class SomeClass extends UtilsBase {
  someClassMethod() {
    this.customUtil() // successfully outputs the whole class in the console
  }
}

// alternatively, you can use the Mixin with an unnamed class
export default class SomeClass extends WithUtils(class {}) {
  someClassMethod() {
    this.customUtil() // successfully outputs the whole class in the console
  }
}

如何为 class 创建实用程序

How to create a util for the class

typescript

vue-class-components