el-checkbox 组件源码解析

checkbox 源码

<template>
<!-- 使用label标签可以将点击事件聚焦到input上 -->
  <label
    class="el-checkbox"
    :class="[
      border && checkboxSize ? 'el-checkbox--' + checkboxSize : '',
      { 'is-disabled': isDisabled },
      { 'is-bordered': border },
      { 'is-checked': isChecked }
    ]"
    :id="id"
  >
    <span class="el-checkbox__input"
      :class="{
        'is-disabled': isDisabled,
        'is-checked': isChecked,
        'is-indeterminate': indeterminate,
        'is-focus': focus
      }"
      :tabindex="indeterminate ? 0 : false"
      :role="indeterminate ? 'checkbox' : false"
      :aria-checked="indeterminate ? 'mixed' : false"
    >
      <!-- 重新定义复选框元素 -->
      <span class="el-checkbox__inner"></span>
      <input
        v-if="trueLabel || falseLabel"
        class="el-checkbox__original"
        type="checkbox"
        :aria-hidden="indeterminate ? 'true' : 'false'"
        :name="name"
        :disabled="isDisabled"
        :true-value="trueLabel"
        :false-value="falseLabel"
        v-model="model"
        @change="handleChange"
        @focus="focus = true"
        @blur="focus = false">
      <input
        v-else
        class="el-checkbox__original"
        type="checkbox"
        :aria-hidden="indeterminate ? 'true' : 'false'"
        :disabled="isDisabled"
        :value="label"
        :name="name"
        v-model="model"
        @change="handleChange"
        @focus="focus = true"
        @blur="focus = false">
    </span>
    <span class="el-checkbox__label" v-if="$slots.default || label">
      <slot></slot>
      <template v-if="!$slots.default">{{label}}</template>
    </span>
  </label>
</template>
<script>
  import Emitter from 'element-ui/src/mixins/emitter';

  export default {
    name: 'ElCheckbox',

    mixins: [Emitter],

    inject: {
      elForm: {
        default: ''
      },
      elFormItem: {
        default: ''
      }
    },

    componentName: 'ElCheckbox',

    data() {
      return {
        selfModel: false,
        focus: false,
        isLimitExceeded: false
      };
    },

    computed: {
      model: {
        get() {
          return this.isGroup
            ? this.store : this.value !== undefined
              ? this.value : this.selfModel;
        },

        set(val) {
          // 如果有ElCheckboxGroup，要判断选中值的个数
          if (this.isGroup) {
            this.isLimitExceeded = false; // 个数超过范围的标识
            (this._checkboxGroup.min !== undefined &&
              val.length < this._checkboxGroup.min &&
              (this.isLimitExceeded = true)); // 短路逻辑可以这样赋值

            (this._checkboxGroup.max !== undefined &&
              val.length > this._checkboxGroup.max &&
              (this.isLimitExceeded = true));

            // 不超出范围，向上emit
            this.isLimitExceeded === false &&
            this.dispatch('ElCheckboxGroup', 'input', [val]); // 触发ElCheckboxGroup组件中的input事件
          } else {
            this.$emit('input', val);
            this.selfModel = val;
          }
        }
      },

      isChecked() {
        if ({}.toString.call(this.model) === '[object Boolean]') {
          // 如果this.model是布尔值类型，直接返回
          return this.model;
        } else if (Array.isArray(this.model)) {
          // 如果this.model是数组类型（说明使用了el-checkbox-group），此时如果包含label的值就说明此el-checkbox被选中，反之没被选中
          return this.model.indexOf(this.label) > -1;
        } else if (this.model !== null && this.model !== undefined) {
          // 如果this.model不是布尔值，数组，null，undefined，那就剩下string，number
          return this.model === this.trueLabel;
        }
      },

      // 判断是否用了el-checkbox-group包裹
      isGroup() {
        let parent = this.$parent;
        while (parent) {
          if (parent.$options.componentName !== 'ElCheckboxGroup') {
            // 如果父组件name不是ElCheckboxGroup，继续向上找
            parent = parent.$parent;
          } else {
            // 如果父组件name是ElCheckboxGroup，把父组件实例赋值给_checkboxGroup
            // 在计算属性中也可以赋值
            this._checkboxGroup = parent;
            return true;
          }
        }
        return false;
      },

      store() {
        // 优先取ElCheckboxGroup中的value，其次取本组件中的value
        return this._checkboxGroup ? this._checkboxGroup.value : this.value;
      },

      /* used to make the isDisabled judgment under max/min props */
      /* 如果使用checkbox-group，要根据max和mix属性判断checkbox的disabled状态 */
      isLimitDisabled() {
        const { max, min } = this._checkboxGroup;
        // 如果没有max并且没有mix，那么不做disabled限制
        return !!(max || min) &&
          // 如果已选的个数等于max了，并且当前checkbox没被选中，那么该checkbox不能被选，禁用掉
          (this.model.length >= max && !this.isChecked) ||
          // 如果已选的个数等于mix了，并且当前checkbox被选了，那么该checkbox不能被勾掉，禁用掉
          (this.model.length <= min && this.isChecked);
      },

      isDisabled() {
        // 这里的this.elForm是从form.vue组件中注入的
        return this.isGroup
          ? this._checkboxGroup.disabled || this.disabled || (this.elForm || {}).disabled || this.isLimitDisabled
          : this.disabled || (this.elForm || {}).disabled;
      },

      _elFormItemSize() {
        // 从form-item组件中注入的elFormItem
        return (this.elFormItem || {}).elFormItemSize;
      },

      checkboxSize() {
        // 先取本组件的size
        // 再取form-item组件（见packages/form/src/form-item.vue）中provide过来的size
        // 最后取Vue.prototype.$ELEMENT（见src/index.js）上的size
        const temCheckboxSize = this.size || this._elFormItemSize || (this.$ELEMENT || {}).size;
        return this.isGroup
          ? this._checkboxGroup.checkboxGroupSize || temCheckboxSize
          : temCheckboxSize;
      }
    },

    props: {
      value: {},
      label: {},
      indeterminate: Boolean,
      disabled: Boolean,
      checked: Boolean,
      name: String,
      trueLabel: [String, Number], // 当选中时的值
      falseLabel: [String, Number], //  当未被选中时的值
      id: String, /* 当indeterminate为真时，为controls提供相关连的checkbox的id，表明元素间的控制关系*/
      controls: String, /* 当indeterminate为真时，为controls提供相关连的checkbox的id，表明元素间的控制关系*/
      border: Boolean,
      size: String
    },

    methods: {
      addToStore() {
        if (
          Array.isArray(this.model) &&
          this.model.indexOf(this.label) === -1
        ) {
          this.model.push(this.label);
        } else {
          this.model = this.trueLabel || true;
        }
      },
      handleChange(ev) {
        // 如果个数超出范围 直接返回
        if (this.isLimitExceeded) return;
        let value;
        if (ev.target.checked) {
          value = this.trueLabel === undefined ? true : this.trueLabel;
        } else {
          value = this.falseLabel === undefined ? false : this.falseLabel;
        }
        this.$emit('change', value, ev);
        this.$nextTick(() => {
          if (this.isGroup) {
            this.dispatch('ElCheckboxGroup', 'change', [this._checkboxGroup.value]);
          }
        });
      }
    },

    created() {
      this.checked && this.addToStore();
    },
    mounted() { // 为indeterminate元素 添加aria-controls 属性
      if (this.indeterminate) {
        // 以aria-开头的都是无障碍浏览属性
        this.$el.setAttribute('aria-controls', this.controls);
      }
    },

    watch: {
      value(value) {
        this.dispatch('ElFormItem', 'el.form.change', value);
      }
    }
  };
</script>

mixins emitter

function broadcast(componentName, eventName, params) {
  this.$children.forEach(child => {
    var name = child.$options.componentName;

    if (name === componentName) {
      child.$emit.apply(child, [eventName].concat(params));
    } else {
      broadcast.apply(child, [componentName, eventName].concat([params]));
    }
  });
}
export default {
  methods: {
    // 向上找到componentName组件 触发eventName事件
    dispatch(componentName, eventName, params) {
      var parent = this.$parent || this.$root;
      var name = parent.$options.componentName;

      // 如果有parent并且，没有name或者name不等于componentName 进入while
      // 终止条件是没有parent或者name等于componentName
      // 当然没有parent什么也不做
      while (parent && (!name || name !== componentName)) {
        parent = parent.$parent;

        if (parent) {
          name = parent.$options.componentName;
        }
      }
      if (parent) {
        // 找到componentName组件后，触发eventName事件
        parent.$emit.apply(parent, [eventName].concat(params));
      }
    },

    // 向下找到componentName组件，触发eventName事件
    broadcast(componentName, eventName, params) {
      broadcast.call(this, componentName, eventName, params);
    }
  }
};

checkbox-group 源码

<script>
  import Emitter from 'element-ui/src/mixins/emitter';

  export default {
    name: 'ElCheckboxGroup',

    componentName: 'ElCheckboxGroup',

    mixins: [Emitter],

    inject: {
      elFormItem: {
        default: ''
      }
    },

    props: {
      value: {},
      disabled: Boolean,
      min: Number,
      max: Number,
      size: String,
      fill: String,
      textColor: String
    },

    computed: {
      _elFormItemSize() {
        return (this.elFormItem || {}).elFormItemSize;
      },
      checkboxGroupSize() {
        return this.size || this._elFormItemSize || (this.$ELEMENT || {}).size;
      }
    },

    watch: {
      value(value) {
        this.dispatch('ElFormItem', 'el.form.change', [value]);
      }
    }
  };
</script>

<template>
  <div class="el-checkbox-group" role="group" aria-label="checkbox-group">
    <slot></slot>
  </div>
</template>

辅助阅读

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