Redux 中间件无限循环？

Question

在下面代码的 sn-p 中，我很难理解 result = next(action) 如何最终不会成为无限循环。由于“最后一个函数”action => 采用参数 action 并根据采用 next 参数 (next => action =>) 的函数计算 result 值，然后调用采用 action 参数的函数 ( next => action =>) 再次。

基本上这段代码的递归性很难理解。

import C from '../constants'
import appReducer from './reducers'
import { createStore, applyMiddleware } from 'redux'

const consoleMessages = store => next => action => {

    let result

    console.groupCollapsed(`dispatching action => ${action.type}`)
    console.log('ski days', store.getState().allSkiDays.length)
    result = next(action)

    let { allSkiDays, goal, errors, resortNames } = store.getState()

    console.log(`

        ski days: ${allSkiDays.length}
        goal: ${goal}
        fetching: ${resortNames.fetching}
        suggestions: ${resortNames.suggestions}
        errors: ${errors.length}

    `)

    console.groupEnd()

    return result

}

export default (initialState={}) => {
    return applyMiddleware(consoleMessages)(createStore)(appReducer, initialState)

Answer 1

next 不是您的 函数之一的名称，它是参数名称。

调用next 不会调用action => {...} 函数。

这里没有任何递归。

重写代码可能会让你更清楚：

function consoleMessages(store) {
  return function (next) {
    return function (action) {
      ...
      let result = next(action)
      ...
    }
  }
}