Vue中extends继承和组件复用性详解

new Vue({
  router,
  store,
  render: h => h(App)
}).$mount('#app')

/**
       * Class inheritance
       */
      Vue.extend = function (extendOptions) {
          extendOptions = extendOptions || {};//外部配置项-即：Vue组件的选项配置
          console.log(extendOptions)
          var Super = this;//指向Vue自身实例的引用
          var SuperId = Super.cid;
          var cachedCtors = extendOptions._Ctor || (extendOptions._Ctor = {});
          if (cachedCtors[SuperId]) {
              return cachedCtors[SuperId];
          }
          var name = getComponentName(extendOptions) || getComponentName(Super.options);
          if (name) {
              validateComponentName(name);
          }
          var Sub = function VueComponent(options) {
              this._init(options);
          };
          Sub.prototype = Object.create(Super.prototype);
          Sub.prototype.constructor = Sub;
          Sub.cid = cid++;
          Sub.options = mergeOptions(Super.options, extendOptions);
          Sub['super'] = Super;
          // For props and computed properties, we define the proxy getters on
          // the Vue instances at extension time, on the extended prototype. This
          // avoids Object.defineProperty calls for each instance created.
          if (Sub.options.props) {
              initProps(Sub);
          }
          if (Sub.options.computed) {
              initComputed(Sub);
          }
          // allow further extension/mixin/plugin usage
          Sub.extend = Super.extend;
          Sub.mixin = Super.mixin;
          Sub.use = Super.use;
          // create asset registers, so extended classes
          // can have their private assets too.
          ASSET_TYPES.forEach(function (type) {
              Sub[type] = Super[type];
          });
          // enable recursive self-lookup
          if (name) {
              Sub.options.components[name] = Sub;
          }
          // keep a reference to the super options at extension time.
          // later at instantiation we can check if Super's options have
          // been updated.
          Sub.superOptions = Super.options;
          Sub.extendOptions = extendOptions;
          Sub.sealedOptions = extend({}, Sub.options);
          // cache constructor
          cachedCtors[SuperId] = Sub;
          return Sub;
      }

    /**
     * 方式1-Vue.extend-使用基础 Vue 构造器，创建一个组件
     * PS：此种方式中,data必须为函数
     * */
    const IButton = Vue.extend({
      name: "IButton",
      template: `<button class="btn" @click="clickBtnHandler($event)">Click</button>`,
      methods: {
        clickBtnHandler(e) {
          console.log(e.target.dataset)
        }
      },
    })
    Vue.component('i-button', IButton);//Vue.component用途之一：将组件注册到全局环境

    /**
     * 方式2-Vue.component-间接调用Vue.extend，创建一个组件
     * PS：此种方式中,data必须为函数
     * */
    const IList = Vue.component('i-list', {
      template: `<div>
        <p>列表</p>
        <ul>
          <li v-for="n in number">{{n}}</li>
        </ul></div>`,
      data: function () {
        return {
          number: 5
        }
      }
    })
    // Vue.component('i-list', IList);//Vue.component创建的组件无需再注册

 //方式3：基于渲染函数构造函数式组件-[基于slot插槽方式提供组件内容1]
    const ITitle = Vue.component(
      "i-title",
      {
      render: function (createElement) {
        return createElement(
          'h' + this.level,   // 标签名称
          this.$slots.default // 子节点数组
        )
      },
      props: {
        level: {
          type: Number,
          required: true
        }
      }
    });

    //方式4-通过对象的形式定义组件-这也是我们在Vue前端应用开发中最常使用的方式,然后通过export default导出
    const InfoBox = {
      name: "InfoBox",
      template: `<div class="box" :style="styleObject">{{content}}</div>`,
      data() {
        return {
          content: '消息内容',
          styleObject: {
            boxSizing: "border-box",
            padding: "25px",
            width: '300px',
            height: '200px',
            backgroundColor: 'rgba(0,0,0,0.3)'
          }
        }
      }
    }
    Vue.component('info-box', InfoBox);//Vue.component用途之一：将组件注册到全局环境

<!--
 * @Description: IList列表组件,基于事件委托机制对列表事件回调做了优化处理
 * @Author: Xwd
 * @Date: 2023-02-16 00:21:49
 * @LastEditors: Xwd
 * @LastEditTime: 2023-02-19 17:03:25
 * @Attention: 此列表组件的clickHandler()点击事件默认基于index下标来选择性的返回item的值,在一些场景下存在风险-->
<template>
  <div class="i-list">
    <p v-if="!!title" class="i-title">{{ title }}</p>
    <!-- <div class="split-horizon"></div> -->
    <div v-if="(list || []).length > 0" class="i-content" @click="clickHandler($event)">
      <div class="i-item" v-for="(item, index) in list" :key="index">
        <img class="i-item-icon" :src="item.image || noImage" />
        <div class="i-item-body">
          <div class="i-item-title">{{ item.title }}<span class="iconfont" title="地图定位" :data-id="item.id"
              :data-index="index">&#xe75d;</span></div>
          <div class="i-item-desc" :title="item.desc">{{ item.desc }}</div>
        </div>
      </div>
    </div>
  </div>
</template>
<script>
import noImage from '@/assets/images/no.png';
export default {
  name: "IList",
  props: {
    title: {
      type: String,
      required: false,
      default: "",
    },
    list: {
      type: Array,
      required: false,
      default: () => [],
    }
  },
  mounted() { },
  methods: {
    /**
     * 列表元素点击事件-回调函数
     * @param {*} event 
     */
    clickHandler(event) {
      const index = event.target.dataset.index;
      if (typeof index !== "undefined" && index !== null) {
        this.$emit("click", this.list[Number(index)], Number(index));
      }
    }
  }
}
</script>
<style lang="less" scoped>
 
</style>

<!--
 * @Description: 
 * @Author: Xwd
 * @Date: 2023-02-19 16:50:16
 * @LastEditors: Xwd
 * @LastEditTime: 2023-02-19 16:56:57
-->
<script>
import IList from '@/components/layout/IList.vue';
export default {
  name:"TownList",
  extends:IList,
  methods:{
     /**
     * 列表元素点击事件-回调函数,覆写父组件方法,基于元素id值重定义处理逻辑
     * @param {*} event 事件对象
     */
     clickHandler(event) {
      const id = event.target.dataset.id;
      console.log(`id=${id}`)
      if (typeof id !== "undefined" && id !== null) {
        const dataIndex = this.list.findIndex(item => item.id == id);
        dataIndex !== -1 & this.$emit("click", this.list[dataIndex], dataIndex)
      }
    }
  }
}
</script>