从 Vue Class 观察器内部的组件装饰器访问方法

Question

基本上我有与 Github 上的 this and this 问题相同的问题，不幸的是，这两个问题在得到回答之前都已关闭：/

我将 Vue 与 Typscript 和 Vue Class 组件一起使用。我需要做的是从 @Component 装饰器内的观察者内部访问我的 (Vue-) Class 的方法。我知道可以使用 this.$data 访问组件的数据，但是方法呢。

我的代码在运行时运行，但在 vscode 中产生编译时错误和错误（属性 'clearInfo' 在类型 'Vue' 上不存在。”）；

@Component({
  watch: {
    firstMesh(newMesh) {
      if (newMesh === undefined) this.clearInfo(1);   // this produces the errors
      else this.showMeshInfo(newMesh, 1);
    },
    secondMesh(newMesh) {
      if (newMesh === undefined) this.clearInfo(2);
      else this.showMeshInfo(newMesh, 2);
    },
  },
})


export default class Info extends Vue {
  clearInfo(whichMesh : number) {
...
  }

  showMeshInfo(mesh : any, index : number) {
    ....
  }


}

Answer 1

您有两个选择：

在 class 自身中定义手表

// first you need to install vue-property-decorators with npm i -S vue-property-decorator
// This library has a lot of useful decorators. You can read more about it here: https://github.com/kaorun343/vue-property-decorator

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


@Component
export default class Info extends Vue {
  @Watch('firstMesh')
  public watchFirstMesh(newValue) {
     // ... do whatever you need to do with the newValue here
  }

  @Watch('secondMesh')
  public watchSecondMesh(newValue) {
     // ... do whatever you need to do with the newValue here
  }
}

在@Component 的选项部分定义监视和方法

@Component({
  watch: {
    firstMesh(newMesh) {
      if (newMesh === undefined) this.clearInfo(1);   // this produces the errors
      else this.showMeshInfo(newMesh, 1);
    },
    secondMesh(newMesh) {
      if (newMesh === undefined) this.clearInfo(2);
      else this.showMeshInfo(newMesh, 2);
    },
  },
  methods: {
   clearInfo(whichMesh : number) {
     ...
   },
   showMeshInfo(mesh : any, index : number) {
     ....
   }   
  }
})
export default class Info extends Vue {
  // Now you need to tell to typescript that there will be a method inside this class called clearInfo and showMeshInfo
  public clearInfo!: (wichMesh: number) => void;
  public showMeshInfo!: (mesh: any, index: number) => void;
}

说明

可以在我离开的 link 上阅读解释
由于您在装饰器 @Component({...}) 中定义了选项，所以这将在实例化 class 的上下文中可用。 Typescript 不知道什么是可用的（我们希望它是那么聪明）。你必须告诉它，这就是为什么我们有 public clearInfo!: (wichMesh: number) => void; 部分。如果你不知道这个语法是什么意思我就简单的解释一下，最后留一个link：

public clearInfo!: (wichMesh: number) => void;

the ! part is called the non-null assertion operator. It is a way to tell the compiler "this expression cannot be null or undefined here, so don't complain about the possibility of it being null or undefined."

The (wichMesh: number) => void; is the function signature. Basically it says: this will be a function that receives as the first argument a number (whichMesh) and returns void (=> void)

Non null assertion typescript Function signature typescript

从 Vue Class 观察器内部的组件装饰器访问方法

Access Method from Vue Class Component Decorator inside a Watcher

javascript

typescript

vue.js

vue-class-components