blocks|key|1363984|text|这就是“选择器”函数的用途。你把整个州树传递给他们，他们就会返回一些州的一部分。调用选择器的代码不需要知道数据的状态在哪里，只需要知道它是返回的。有关一些示例，请参见http://redux.js.org/docs/recipes/ComputingDerivedData.html。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1363985|在saga中，可以使用API接口来执行选择器。|1363986|entityMap|0|LINK|mutability|MUTABLE|url|http://redux.js.org/docs/recipes/ComputingDerivedData.html|1|https://github.com/redux-saga/redux-saga/tree/master/docs/api#selectselector-args^0|2B|1M|0|0|B|5|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

This is what "selector" functions are for. You pass them the entire state tree, and they return some piece of the state. The code that calls the selector doesn't need to know where in the state that data was, just that it was returned. See <a href="http://redux.js.org/docs/recipes/ComputingDerivedData.html" rel="noreferrer">http://redux.js.org/docs/recipes/ComputingDerivedData.html</a> for some examples.

Within a saga, the <a href="https://github.com/redux-saga/redux-saga/tree/master/docs/api#selectselector-args" rel="noreferrer"><code>select()</code> API</a> can be used to execute a selector.

blocks|key|1364011|text|正如@markerikson已经说过的那样，redux-saga公开了一个非常有用的API+select()来调用状态中的selector，以便在传奇中获得它的某些部分。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1364012|对于您的示例，一个简单的实现可以是：|1364013|/*
+*+Selector.+The+query+depends+by+the+state+shape
+*/
export+const+getProject+=+(state)+=>+state.project

//+Saga
export+function*+saveProjectTask()+{
++while(true)+{
++++yield+take(SAVE_PROJECT);
++++let+project+=+yield+select(getProject);+//+<--+get+the+project
++++yield+call(fetch,+'/api/project',+{+body:+project,+method:+'PUT'+});
++++yield+put({type:+SAVE_PROJECT_SUCCESS});
++}
}|code-block|syntax|javascript|1364014|除了@markerikson建议的文档之外，D.Abramov还提供了一个非常好的视频教程，它解释了如何在Redux中使用selectors。还可以在Twitter上查看这有趣的帖子。|1364015|entityMap|0|LINK|mutability|MUTABLE|url|https://redux-saga.js.org/docs/api/#selectselector-args|1|http://redux.js.org/docs/recipes/ComputingDerivedData.html|2|https://egghead.io/lessons/javascript-redux-colocating-selectors-with-reducers|3|https://twitter.com/dan_abramov/status/664581975764766721^0|M|A|1A|8|1P|8|1A|8|0|0|0|0|1P|9|H|2|1|15|4|2|2D|1|3|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|F|3|G|5|6|7|1C|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@$9|1H|A|1I|1|1J]|$9|1K|A|1L|1|1M]|$9|1N|A|1O|1|1P]]|E|$]]|$1|O|3|-4|5|6|7|1Q|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]|Y|$5|R|S|T|E|$U|Z]]|10|$5|R|S|T|E|$U|11]]]]

As @markerikson already says, <code>redux-saga</code> exposes a very useful API <a href="https://redux-saga.js.org/docs/api/#selectselector-args" rel="noreferrer"><code>select()</code></a> to invoke a <code>selector</code> on the state for getting some part of it available inside the saga. 

For your example a simple implementation could be:

<pre><code>/*
 * Selector. The query depends by the state shape
 */
export const getProject = (state) =&gt; state.project

// Saga
export function* saveProjectTask() {
 while(true) {
 yield take(SAVE_PROJECT);
 let project = yield select(getProject); // &lt;-- get the project
 yield call(fetch, '/api/project', { body: project, method: 'PUT' });
 yield put({type: SAVE_PROJECT_SUCCESS});
 }
}
</code></pre>

In addition to the suggested <a href="http://redux.js.org/docs/recipes/ComputingDerivedData.html" rel="noreferrer">doc</a> by @markerikson, there is a very good <a href="https://egghead.io/lessons/javascript-redux-colocating-selectors-with-reducers" rel="noreferrer">video tutorial</a> by D. Abramov which explains how to use <code>selectors</code> with Redux. Check also <a href="https://twitter.com/dan_abramov/status/664581975764766721" rel="noreferrer">this</a> interesting thread on Twitter.

blocks|key|1087127|text|我使用一个eventChannel来分派生成器函数中回调的动作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1087128|import+{eventChannel}+from+'redux-saga';
import+{call,+take}+from+'redux-saga/effects';

function+createEventChannel(setEmitter)+{
++++return+eventChannel(emitter+=>+{
++++++++setEmitter(emitter)
++++++++return+()+=>+{

++++++++}
++++++}
++++)
}

function*+YourSaga(){
++++let+emitter;
++++const+internalEvents+=+yield+call(createEventChannel,+em+=>+emitter+=+em)

++++const+scopedCallback+=+()+=>+{
++++++++emitter({type,+payload})
++++}

++++while(true){
++++++++const+action+=+yield+take(internalEvents)
++++++++yield+put(action)
++++}
}|code-block|syntax|javascript|1087129|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I used an eventChannel to dispatch an action from a callback within the generator function

<pre><code>import {eventChannel} from 'redux-saga';
import {call, take} from 'redux-saga/effects';

function createEventChannel(setEmitter) {
 return eventChannel(emitter =&gt; {
 setEmitter(emitter)
 return () =&gt; {

 }
 }
 )
}

function* YourSaga(){
 let emitter;
 const internalEvents = yield call(createEventChannel, em =&gt; emitter = em)

 const scopedCallback = () =&gt; {
 emitter({type, payload})
 }

 while(true){
 const action = yield take(internalEvents)
 yield put(action)
 }
}
</code></pre>

How do I access the redux state inside a saga function?

Short answer:

<pre><code>import { select } from 'redux-saga/effects';
...
let data = yield select(stateSelectorFunction);
</code></pre>

How to get something from the state / store inside a redux-saga function?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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如何访问saga函数中的redux状态？简短回答：import { select } from 'redux-saga/effects';...let data = yield select(stateSelectorFunction);

问如何从状态/商店中得到一些东西，在一个redux-saga函数中？
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问如何从状态/商店中得到一些东西，在一个redux-saga函数中？EN