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  • redux reducer笔记

    踩坑一,reducer过于抽象

    reducer写得没那么抽象也不会有人怪你的。_

    reducer其实只有一个,由不同的reducer composition出来的。所以,

    1. reducer的父作用域是共享的
    2. 某一个action被发出后,会在reducer中进行查找出来的reducer代码

    例如:

    //reducer01.js
    const disposeFetchRandom = (preState = {}, action) => {
      switch (action.type) {
        case `${REQUEST_BEGIN}${action.condition}`:
        case `${RECEIVED}${action.condition}`:
        case `${RECEIVE_FAILED}${action.condition}`:
          //do something to state
        default:
          return preState;
      }
    }
    

    //reducer02.js
    const disposeCategories = (preState = {}, action) => {
      let condition = action.condition
      switch (action.type) {
        case `${REQUEST_BEGIN}${condition}`:
        case `${RECEIVED}${condition}`:
        case `${RECEIVE_FAILED}${condition}`:
          //do something
        default:
          return preState
      }
    }
    

    针对上面两个Reducer:

    1. dispatch({type: "REQUEST_BEGIN_RANDOM"})时,reducer01.jsreducer02.js都会对其进行处理
    2. 无法处理dispatch({type: "REQUEST_BEGIN_RANDOM})dispatch({type: "REQUEST_BEGIN_CATEGORIES"})这两个action
    3. 解决办法。改为(以reducer01.js为例)
    //reducer01.js
    const RANDOM = "_RANDOM";
    const disposeFetchRandom = (preState = {}, action) => {
      switch (action.type) {
        case REQUEST_BEGIN + RANDOM://必须明确指定action.type
        case RECEIVED + RANDOM:
        case RECEIVE_FAILED + RANDOM:
          //do something to state
        default:
          return preState;
      }
    }
    
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  • 原文地址:https://www.cnblogs.com/looyulong/p/9411150.html
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