ts装饰器写法

2020-03-04 本文已影响0人郑馋师

今天做项目的时候发现要用到watch来监听，所以就学习了watch的装饰器写法，然后顺便把之前用过的都看了，这里做一个简单的回顾

类型

多种装饰器和一个函数（Mixins）

@Prop
@PropSync
@Model
@Watch
@Provide
@Inject
@ProvideReactive
@InjectReactive
@Emit
@Ref
@Component (由 vue-class-component提供)
Mixins (辅助函数名为 mixins，由 vue-class-component提供)

@Prop

@Prop(options: (PropOptions | Constructor[] | Constructor) = {})

import { Vue, Component, Prop } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @Prop(Number) readonly propA: number | undefined
  @Prop({ default: 'default value' }) readonly propB!: string
  @Prop([String, Boolean]) readonly propC: string | boolean | undefined
}

相当于

export default {
  props: {
    propA: {
      type: Number
    },
    propB: {
      default: 'default value'
    },
    propC: {
      type: [String, Boolean]
    }
  }
}

Tips:

如果要type根据类型定义设置每个prop值的属性，则可以使用reflect-metadata。

设置emitDecoratorMetadata到true。
导入reflect-metadata 之前先导入vue-property-decorator（reflect-metadata只需导入一次。）

import 'reflect-metadata'
import { Vue, Component, Prop } from 'vue-property-decorator'

@Component
export default class MyComponent extends Vue {
  @Prop() age!: number
}

每个 prop's 默认值需要定义为与上面显示的示例代码相同。

不支持 @Prop() prop = 'default value' .

@PropSync

@PropSync(propName: string, options: (PropOptions | Constructor[] | Constructor) = {})

import { Vue, Component, PropSync } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @PropSync('name', { type: String }) syncedName!: string
}

相当于

export default {
  props: {
    name: {
      type: String
    }
  },
  computed: {
    syncedName: {
      get() {
        return this.name
      },
      set(value) {
        this.$emit('update:name', value)
      }
    }
  }
}

除此之外，它的工作方式与@Prop将propName作为装饰器的参数的工作方式不同，此外，它还在幕后创建了一个计算的getter和setter。这样可以与该属性进行交互，因为它是常规数据属性，同时使其与.sync在父组件中附加修饰符一样容易。这个装饰器其实个人认为用处不是那么大，毕竟直接使用修饰符就好。

@Model

@Model(event?: string, options: (PropOptions | Constructor[] | Constructor) = {})

import { Vue, Component, Model } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @Model('change', { type: Boolean }) readonly checked!: boolean
}

相当于

export default {
  model: {
    prop: 'checked',
    event: 'change'
  },
  props: {
    checked: {
      type: Boolean
    }
  }
}

@Modelproperty也可以通过定义其类型定义中的属性reflect-metadata设置type。

@Watch

@Watch(path: string, options: WatchOptions = {}) decorator

import { Vue, Component, Watch } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @Watch('child')
  onChildChanged(val: string, oldVal: string) {}

  @Watch('person', { immediate: true, deep: true })
  onPersonChanged1(val: Person, oldVal: Person) {}

  @Watch('person')
  onPersonChanged2(val: Person, oldVal: Person) {}
}

相当于

export default {
  watch: {
    child: [
      {
        handler: 'onChildChanged',
        immediate: false,
        deep: false
      }
    ],
    person: [
      {
        handler: 'onPersonChanged1',
        immediate: true,
        deep: true
      },
      {
        handler: 'onPersonChanged2',
        immediate: false,
        deep: false
      }
    ]
  },
  methods: {
    onChildChanged(val, oldVal) {},
    onPersonChanged1(val, oldVal) {},
    onPersonChanged2(val, oldVal) {}
  }
}

@Provide

@Provide(key?: string | symbol) / @Inject(options?: { from?: InjectKey, default?: any } | InjectKey) decorator

import { Component, Inject, Provide, Vue } from 'vue-property-decorator'

const symbol = Symbol('baz')

@Component
export class MyComponent extends Vue {
  @Inject() readonly foo!: string
  @Inject('bar') readonly bar!: string
  @Inject({ from: 'optional', default: 'default' }) readonly optional!: string
  @Inject(symbol) readonly baz!: string

  @Provide() foo = 'foo'
  @Provide('bar') baz = 'bar'
}

相当于

const symbol = Symbol('baz')

export const MyComponent = Vue.extend({
  inject: {
    foo: 'foo',
    bar: 'bar',
    optional: { from: 'optional', default: 'default' },
    [symbol]: symbol
  },
  data() {
    return {
      foo: 'foo',
      baz: 'bar'
    }
  },
  provide() {
    return {
      foo: this.foo,
      bar: this.baz
    }
  }
})

@ProvideReactive

@ProvideReactive(key?: string | symbol) / @InjectReactive(options?: { from?: InjectKey, default?: any } | InjectKey) decorator

这些是 @Provide和 @Inject的被动版本.如果提供的值被父组件修改，则子组件可以捕获此修改。

const key = Symbol()
@Component
class ParentComponent extends Vue {
  @ProvideReactive() one = 'value'
  @ProvideReactive(key) two = 'value'
}

@Component
class ChildComponent extends Vue {
  @InjectReactive() one!: string
  @InjectReactive(key) two!: string
}

@Emit

@Emit(event?: string)

The functions decorated by @Emit $emit their return value followed by their original arguments. If the return value is a promise, it is resolved before being emitted.
这个函数是由@Emit $emit他们的返回值和原始参数所修饰的。如果返回值是一个promise，则在返回之前将其解析。

如果未通过event参数提供事件的名称，则使用函数名称。在这种情况下，camelCase名称将转换为kebab-case。

import { Vue, Component, Emit } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  count = 0

  @Emit()
  addToCount(n: number) {
    this.count += n
  }

  @Emit('reset')
  resetCount() {
    this.count = 0
  }

  @Emit()
  returnValue() {
    return 10
  }

  @Emit()
  onInputChange(e) {
    return e.target.value
  }

  @Emit()
  promise() {
    return new Promise(resolve => {
      setTimeout(() => {
        resolve(20)
      }, 0)
    })
  }
}

相当于

export default {
  data() {
    return {
      count: 0
    }
  },
  methods: {
    addToCount(n) {
      this.count += n
      this.$emit('add-to-count', n)
    },
    resetCount() {
      this.count = 0
      this.$emit('reset')
    },
    returnValue() {
      this.$emit('return-value', 10)
    },
    onInputChange(e) {
      this.$emit('on-input-change', e.target.value, e)
    },
    promise() {
      const promise = new Promise(resolve => {
        setTimeout(() => {
          resolve(20)
        }, 0)
      })

      promise.then(value => {
        this.$emit('promise', value)
      })
    }
  }
}

@Ref

@Ref(refKey?: string) decorator

import { Vue, Component, Ref } from 'vue-property-decorator'

import AnotherComponent from '@/path/to/another-component.vue'

@Component
export default class YourComponent extends Vue {
  @Ref() readonly anotherComponent!: AnotherComponent
  @Ref('aButton') readonly button!: HTMLButtonElement
}

相当于

export default {
  computed() {
    anotherComponent: {
      cache: false,
      get() {
        return this.$refs.anotherComponent as AnotherComponent
      }
    },
    button: {
      cache: false,
      get() {
        return this.$refs.aButton as HTMLButtonElement
      }
    }
  }
}