使用react context 实现vue插槽slot功能

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首先来看下vue的slot的实现

<base-layout>组件，具名插槽name定义以及默认插槽

<div class="container">
 <header>
  <slot name="header"></slot>
 </header>
 <main>
  <slot></slot>
 </main>
 <footer>
  <slot name="footer"></slot>
 </footer>
</div>
<template>

提供内容渲染的组件

<base-layout>
 <template v-slot:header>
  <h1>Here might be a page title</h1>
 </template>
 <p>A paragraph for the main content.</p>
 <p>And another one.</p>
 <template v-slot:footer>
  <p>Here's some contact info</p>
 </template>
</base-layout>

最终会渲染出已下架结构

<base-layout>
 <template v-slot:header>
  <h1>Here might be a page title</h1>
 </template>
 <p>A paragraph for the main content.</p>
 <p>And another one.</p>
 <template v-slot:footer>
  <p>Here's some contact info</p>
 </template>
</base-layout>

言归正传，怎样使用react的context实现vue的这一功能呢

1 首先确认下layout组件的结构

import React, { Component } from 'react';
import SlotProvider from './SlotProvider'
import Slot from './Slot'
class AppLayout extends Component {
 static displayName = 'AppLayout'
 render () {
  return (
   <div className="container">
    <header>
     <Slot name="header"></Slot>
    </header>
    <main>
     <Slot></Slot>
    </main>
    <footer>
     <Slot name="footer"></Slot>
    </footer>
   </div>
  )
 }
}
export default SlotProvider(AppLayout)

2 对此结构输出具体内容的组件

import React, { Component } from 'react';
import AppLayout from './AppLayout'
import AddOn from './AddOn'
export default class App extends Component {
  render() {
    return (
      <AppLayout>
        <AddOn slot="header">
          <h1>这里可能是一个页面标题</h1>
        </AddOn>
        <AddOn>
          <p>主要内容的一个段落。</p>
          <p>另一个段落。</p>
        </AddOn>
        <AddOn slot="footer">
          <p>这里有一些联系信息</p>
        </AddOn>
      </AppLayout>
    )
  }
}

3 其中AddOn类似于上面vue的template，所以下面来实现这个简单的只是用来提供slot标识和children内容的组件AddOn的实现

import React from 'react';
import PropTypes from 'prop-types'
const AddOn = () => null
AddOn.propTypes = { slot: PropTypes.string }
AddOn.defaultTypes = { slot: '$$default' }
AddOn.displayName = 'AddOn'
export default AddOn

4 Slot组件

import React from 'react';
import { SlotContext } from './SlotProvider'
import PropTypes from 'prop-types'
const Slot = ({ name, children }) => {
 return (
  <SlotContext.Consumer>
   {(value) => {
    const addOnRenderer = value.requestAddOnRenderer(name)
     return (addOnRenderer && addOnRenderer()) || children || null
   }}
  </SlotContext.Consumer>
 )
}
Slot.displayName = 'Slot'
Slot.propTypes = { name: PropTypes.string }
Slot.defaultProps = { name: '$$default' }
export default Slot

5 接下来就是对Slot进行解析的HOC SlotProvider组件了

import React, { Component } from 'react';
function getDisplayName(component) {
  return component.displayName || component.name || 'component'
}
export const SlotContext = React.createContext({
  requestAddOnRenderer: () => { }
})
const SlotProviderHoC = (WrappedComponent) => {
  return class extends Component {
    static displayName = `SlotProvider(${getDisplayName(WrappedComponent)})`
    // 用于缓存每个<AddOn />的内容
    addOnRenderers = {}
    requestAddOnRenderer = (name) => {
      if (!this.addOnRenderers[name]) {
        return undefined
      }
      return () => (
        this.addOnRenderers[name]
      )
    }
    render() {
      const {
        children,
        ...restProps
      } = this.props
      if (children) {
        // 以k-v的方式缓存<AddOn />的内容
        const arr = React.Children.toArray(children)
        const nameChecked = []
        this.addOnRenderers = {}
        arr.forEach(item => {
          const itemType = item.type
          console.log('itemType',itemType)
          if (item.type.displayName === 'AddOn') {
            const slotName = item.props.slot || '$$default'
            // 确保内容唯一性
            if (nameChecked.findIndex(item => item === slotName) !== -1) {
              throw new Error(`Slot(${slotName}) has been occupied`)
            }
            this.addOnRenderers[slotName] = item.props.children
            nameChecked.push(slotName)
          }
        })
      }
      return (
        <SlotContext.Provider value={{ requestAddOnRenderer: this.requestAddOnRenderer }}>
          <WrappedComponent {...restProps} />
        </SlotContext.Provider >
      )
    }
  }
 }
 export default SlotProviderHoC

6 最终渲染结果