javascript - 如何修复 Vue 警告 : You may have an infinite update loop in a component render function

Question

我收到以下无限循环警告。我知道这可能是因为由于方法调用，我正在更改模板的 for 循环中的变量。知道如何解决吗？循环确实完成了，所以它实际上不是无限循环，但我想修复警告。

[Vue warn]: You may have an infinite update loop in a component render function.

代码片段:

new Vue({
  el: '#app',
  data: {
    contents: {"34": {"id": 34, build_name: "email_simple", build_readable: "Email"},"35": {"id": 35, build_name: "email_complex", build_readable: "Email"},"36": {"id": 36, build_name: "email_half", build_readable: "Email"}},
    last_build_type: '',
    contents_tree: [34,35,36]
  }, 
  methods: {
      checkBuildType(id){
        let check = false;
        if(this.last_build_type !== this.contents[id].build_name){
            check = true
        }
        this.last_build_type = this.contents[id].build_name;
        return check
      }

  }
  
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <template v-for="(id, i) in contents_tree">
      <div v-bind:key="i + '_' + id" class="inline">
          <template v-if="checkBuildType(id)">
              {{i}} - {{id}} -
              {{contents[id].build_readable}}
              <br>
            
          </template>

    </div>
  </template>
</div>

Answer 1

您收到该警告是因为 Vue 必须为 v-for 循环中的每个项目重新渲染，因为 for 循环会更新组件的状态。我的解决方案是在一个计算属性(基本上是一个索引对象)中一次计算每个数组项的结果，并在 v-for 中访问该计算属性，而不是使用 checkBuildType 方法。

new Vue({
  el: '#app',
  data: {
    contents: {
      "33": {
        "id": 33,
        build_name: "email_half",
        build_readable: "Email"
      },
      "34": {
        "id": 34,
        build_name: "email_simple",
        build_readable: "Email"
      },
      "35": {
        "id": 35,
        build_name: "email_complex",
        build_readable: "Email"
      },
      "36": {
        "id": 36,
        build_name: "email_half",
        build_readable: "Email"
      },
      "37": {
        "id": 37,
        build_name: "email_half",
        build_readable: "Email"
      }
    },
    last_build_type: '',
    contents_tree: [34, 35, 36, 37, 33]
  },
  computed: {
    buildTypes() {
      const buildTypesMap = {};
      for (id of this.contents_tree) {
        buildTypesMap[id] = this.checkBuildType(id);
      }
      return buildTypesMap
    }
  },
  methods: {
    checkBuildType(id) {
      let check = false;
      if (this.last_build_type !== this.contents[id].build_name) {
        check = true
      }
      this.last_build_type = this.contents[id].build_name;
      return check
    }

  }

})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <template v-for="(id, i) in contents_tree">
      <div v-bind:key="i + '_' + id" class="inline">
          <template v-if="buildTypes[id]">
              {{i}} - {{id}} -
              {{contents[id].build_readable}}
              <br>
            
          </template>

</div>
</template>
</div>