redux-saga 中间件

话不多说，先上源码，中间件意味着要满足redux中间件范式

（{state,dispatch}）=>(next)=>(action)=>{

    balaba......

   result=next(action)

   balaba.............

  return result

}

redux-saga也不例外，

function sagaMiddleware({ getState, dispatch }) {

const sagaEmitter = emitter()

sagaEmitter. emit = ( options. emitter || ident)( sagaEmitter. emit)

sagaMiddleware. run = runSaga. bind( null, {

context,

subscribe: sagaEmitter. subscribe,

dispatch,

getState,

sagaMonitor,

logger,

onError,

})

return next => action => {

if ( sagaMonitor && sagaMonitor. actionDispatched) {

sagaMonitor. actionDispatched( action)

}

const result = next( action) // hit reducers

sagaEmitter. emit( action)

return result

}

}

后面主要研究 saga 是如何利用中间件属性来完成异步操作的。

各种effect优先级 及处理函数

return (

// Non declarative effect

is. promise( effect) ? resolvePromise( effect, currCb)

: is. helper( effect) ? runForkEffect( wrapHelper( effect), effectId, currCb)

: is. iterator( effect) ? resolveIterator( effect, effectId, name, currCb)

// declarative effects

: is. array( effect) ? runParallelEffect( effect, effectId, currCb)

: ( data = asEffect. take( effect)) ? runTakeEffect( data, currCb)

: ( data = asEffect. put( effect)) ? runPutEffect( data, currCb)

: ( data = asEffect. all( effect)) ? runAllEffect( data, effectId, currCb)

: ( data = asEffect. race( effect)) ? runRaceEffect( data, effectId, currCb)

: ( data = asEffect. call( effect)) ? runCallEffect( data, effectId, currCb)

: ( data = asEffect. cps( effect)) ? runCPSEffect( data, currCb)

: ( data = asEffect. fork( effect)) ? runForkEffect( data, effectId, currCb)

: ( data = asEffect. join( effect)) ? runJoinEffect( data, currCb)

: ( data = asEffect. cancel( effect)) ? runCancelEffect( data, currCb)

: ( data = asEffect. select( effect)) ? runSelectEffect( data, currCb)

: ( data = asEffect. actionChannel( effect)) ? runChannelEffect( data, currCb)

: ( data = asEffect. flush( effect)) ? runFlushEffect( data, currCb)

: ( data = asEffect. cancelled( effect)) ? runCancelledEffect( data, currCb)

: ( data = asEffect. getContext( effect)) ? runGetContextEffect( data, currCb)

: ( data = asEffect. setContext( effect)) ? runSetContextEffect( data, currCb)

: /* anything else returned as is */ currCb( effect)

)

}