Question

我正在尝试使用ES6类中的迭代器，并且在为我的类创建每个方法时遇到了引用错误：ReferenceError: vertex is not defined。我能够将我的顶点添加到图形中，图形实例将打印出正确的数据。这个迭代器的使用是否正确？

class Vertex {
  constructor(key) {
    this.id = key
    this.connectedTo = {}
  }
}

class Graph {
  constructor() {
    this.vertexList = {}
    this.numVerticies = 0
  }

[Symbol.iterator]() {
     // Reflect.ownKeys() === Object.keys()
  const vertexListKeys = Reflect.ownKeys(this.vertexList)
  let index = 0
  return {
    next: () => {
         // Reflect.get(myObj, key) === Object[key]
      let value = Reflect.get(this.vertexList, vertexListKeys[index])
      index++
      return {
        done: index > vertexListKeys.length ? true : false,
        value: value
        }
      }
    }
  }

// Iterate through vertexList values
 each(callback) {
  for (vertex of this) {
    callback(vertex)
    }
  }

 addVertex(key) {
   const newVertex = new Vertex(key)
     this.vertexList[key] = newVertex
     this.numVerticies++
   return newVertex
  }


}



const graph = new Graph()

for (var i = 0; i < 6; i++) {
  g.addVertex(i)
}


graph.each((vert) => console.log(vert))
// ReferenceError: vertex is not defined
// for (vertex of this) {
//               ^

我也尝试将每个方法更改为生成器，但是当我这样做时，没有任何内容打印到控制台

*each(callback) {
  for(vertex in this) {
    yield callback(vertex) // omitting yield doesn't work either
  }
}

Answer 1

错误就是它所说的

for (vertex of this) {

使用未在任何地方声明的变量vertex。它应该是

for (var vertex of this) {

或let或const。

Answer 2

    class Vertex {
  constructor(key) {
    this.id = key
    this.connectedTo = {}
  }
}

class Graph {
  constructor() {
    this.vertexList = {}
    this.numVerticies = 0
  }

[Symbol.iterator]() {
     // Reflect.ownKeys() === Object.keys()
  const vertexListKeys = Reflect.ownKeys(this.vertexList)
  let index = 0
  return {
    next: () => {
         // Reflect.get(myObj, key) === Object[key]
      let value = Reflect.get(this.vertexList, vertexListKeys[index])
      index++
      return {
        done: index > vertexListKeys.length ? true : false,
        value: value
        }
      }
    }
  }

// Iterate through vertexList values
 each(callback) {
  for (var vertex of this) {
    callback(vertex)
    }
  }

 addVertex(key) {
   const newVertex = new Vertex(key)
     this.vertexList[key] = newVertex
     this.numVerticies++
   return newVertex
  }


}



const g = new Graph()

for (var i = 0; i < 6; i++) {
  g.addVertex(i)
}


g.each((vert) => console.log(vert))

在每个函数中，它应该是var vertex，因为vertex尚未声明。

如何在ES6类方法中使用迭代器

2 个答案: