Vue js：如何在两个组件中使用 mixin 功能？通过执行错误

Question

我有 2 个组件：parent 和 child 以及一个 mixin。我正在尝试在两者中使用一个功能。从父组件中的子组件调用 mixin 函数。这个 mixin 函数还更改了来自父组件的数据 var，它在 props 中引用了子组件。

但是，在这行代码中：

this.modals.filter = 'block'; occurs error: TypeError: Cannot set properties of undefined (setting 'filter')

我不明白为什么，因为道具中已经引用了 modals.filter？

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Test</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.14"></script>
  </head>
  <body>
    <div id="example" style="width:100%;height:100%">
        <parent></parent>
    </div>
  </body>
  <script>
    var myMixin = { 
        methods: {
            powerbiFilterModal: function() {
                this.modals.filter = 'block';
                if (this.embed.channelName, this.filters.columnName, this.filters.tableName) {
                    // Some other functions
                    // ...
                    console.log(this.embed.channelName, this.filters.columnName, this.filters.tableName);
                    // Hide modal
                    this.modals.filter = 'none';
                    // Clear inputs
                    this.embed.channelName = '';
                    this.filters.columnName = '';
                    this.filters.tableName = '';
                }
            }
        }
    };
    Vue.component('child', {
        mixins: [myMixin],
        template: `
        <div :style="{ display: filterOverlay }">
            <span class="close" style="align-self: flex-end; cursor: pointer;" @click="closeModal">x</span>
            <span class="label" style="align-self: center; margin-bottom: 4%">Filter Settings: </span>
            <input type="text" placeholder="Define channel name" v-model.trim="channelName">
            <input type="text" placeholder="Define filter name" v-model.trim="columnName">
            <input type="text" placeholder="Define table to filter" v-model.trim="tableName">
            <button @click="powerbiFilterModal">Subscribe & Send</button>
        </div>
        `,
        props: {
            filterOverlay: {
                type: String,
                required: false,
                default: 'none'
            },
            channelName: {
                type: String,
                required: false
            },
            columnName: {
                type: String,
                required: false
            },
            tableName: {
                type: String,
                required: false
            }   
        },
        methods: {
            closeModal: function() {
                this.$emit('emitEv', 'none');
            }
        }
    });
    
    Vue.component('parent', {
        mixins: [myMixin],
        template: `
            <div>
                <button @click="powerbiFilterModal">Set Filters</button>
                <child @emitEv="changeOverlay" v-bind:filter-overlay="modals.filter">Child</child>
            </div>
        `,
        data: function() {
            return {
                modals: {
                    filter: 'none'
                },
                embed: {
                    channelName: ''
                },
                filters: {
                    columnName: '',
                    tableName: ''
                }
            }
        },
        methods: {
            changeOverlay: function(value) {
                this.modals.filter = value;
            }
        }
    });
    new Vue({
        el: "#example"
    });
  </script>
</html>

Answer 1

powerbiFilterModal()引用了this.modals，在父组件中使用是可以的，但是子组件没有这样的数据，所以在子组件中调用mixin会报错.

Answer 2

解释我的评论

子组件

Vue.component("child", {
  // mixins: [myMixin], remove mixin from child
  template: `
  <div>
      <!-- bla bla bla -->
      <button @click="$emit('fire')">Subscribe & Send</button>
  </div>
  ...
  `
});

父组件

Vue.component("parent", {
  mixins: [myMixin],
  template: `
      <div>
          <button @click="powerbiFilterModal">Set Filters</button>

          <!-- HERE we listen for event (fire) from child and call powerbiFilterModal method from mixin -->
          <child @fire="powerbiFilterModal" @emitEv="changeOverlay" v-bind:filter-overlay="modals.filter">Child</child>
      </div>
  `,
  data: function () {
    return {
      modals: {
        filter: "none"
      },
      embed: {
        channelName: ""
      },
      filters: {
        columnName: "",
        tableName: ""
      }
    };
  },
  methods: {
    changeOverlay: function (value) {
      this.modals.filter = value;
    }
  }
});

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