霍春阳版

2023年09月11日

柏拉文

越努力，越幸运

一、实现

---

1.1 this.$emit

1.2 steup emit

const mountComponent = (vnode, container, anchor) => {
    const componentOptions = vnode.type;
    const {
      data,
      setup,
      props: propsOption,
      render,
      beforeCreate,
      created,
      beforeMount,
      mounted,
      beforeUpdate,
      updated
    } = componentOptions;

    beforeCreate && beforeCreate();

    const state = data ? reactive(data()) : null;
    const [props, attrs] = resolveProps(propsOption, vnode.props);

    /**
     * @description: 组件实例
     */
    const instance = {
      state,
      attrs,
      subTree: null,
      isMounted: false,
      props: shallowReactive(props)
    };

    function emit(event, ...payload) {
      const eventName = `on${event[0].toUpperCase() + event.slice(1)}`;
      const handler = instance.props[eventName];
      if (handler) {
        handler(...payload);
      } else {
        console.log(`${eventName} 事件不存在`);
      }
    }

    const setupContext = { emit, attrs };
    const setupResult = setup(shallowReadonly(instance.props), setupContext);
    let setupState = null;
    if (typeof setupResult === 'function') {
      if (render) {
        console.log('setup 返回值为函数，将作为渲染函数， render 选项将被忽略');
      }
      render = setupResult;
    } else {
      setupState = setupResult;
    }
    vnode.component = instance;

    const renderContext = new Proxy(instance, {
      get(target, key, receiver) {
        const { state, props } = target;
        if (state && key in state) {
          return Reflect.get(state, key, receiver);
        } else if (key in props) {
          return Reflect.get(props, key, receiver);
        } else if (setupState && key in setupState) {
          return Reflect.get(setupState, key, receiver);
        } else {
          console.error(`${key} 不存在`);
          return false;
        }
      },

      set(target, key, value, receiver) {
        const { state, props } = target;
        if (state && key in state) {
          return Reflect.set(state, key, value, receiver);
        } else if (key in props) {
          console.warn(`props 是只读的`);
          return false;
        } else if (key in setupState) {
          return Reflect.set(setupState, key, value, receiver);
        } else {
          console.error(`${key} 不存在`);
          return false;
        }
      }
    });

    created && created.call(renderContext);

    effect(
      () => {
        const subTree = render.call(renderContext, renderContext);
        if (!instance.isMounted) {
          beforeMount && beforeMount.call(renderContext);
          patch(null, subTree, container, anchor);
          instance.isMounted = true;
          mounted && mounted.call(renderContext);
        } else {
          beforeUpdate && beforeUpdate.call(renderContext);
          patch(instance.subTree, subTree, container, anchor);
          updated && updated.call(renderContext);
        }
        instance.subTree = subTree;
      },
      {
        scheduler: queueJob
      }
    );
};

二、测试

---

2.1 this.$emit

2.2 setup emit

const renderOps = {
  setText(el, text) {
    el.nodeValue = text;
  },
  createText(text) {
    return document.createTextNode(text);
  },
  createComment(comment) {
    return document.createComment(comment);
  },
  createElement(tag) {
    return document.createElement(tag);
  },
  setElementText(el, text) {
    el.textContent = text;
  },
  insert(el, parent, anchor = null) {
    parent.insertBefore(el, anchor);
  }
};

const renderer = createRenderer({ ...renderOps, patchProp });

const Component = {
  name: 'MyComponent',
  props: {
    msgProp: String
  },
  data() {
    return {
      msg: '组件内容'
    };
  },
  setup(props, setupContext) {
    const { emit } = setupContext;

    emit('handleChange', 1, 2);

    const obj = reactive({ a: 1, b: 2 });
    return { obj };
  },
  render() {
    return {
      type: 'div',
      shapeFlag: 9,
      children: this.msg + this.msgProp + this.obj.a
    };
  },
  beforeCreate() {
    console.log('beforeCreaate');
  },
  created() {
    console.log('created');
  },
  beforeMount() {
    console.log('beforeMount');
  },
  mounted() {
    console.log('mounted');
  }
};

const vnode = {
  type: Component,
  shapeFlag: 4,
  props: {
    msgProp: '父组件内容',
    onHandleChange: (argu1, argu2) => {
      console.log('自定义事件', argu1, argu2);
    }
  }
};

renderer.render(vnode, document.querySelector('#app'));