Redux-saga source code analysis

1. Why`redux-saga`

Redux-sage is a middleware designed to handle the following side effects (asynchronous tasks). It is a process manager who receives events and may trigger new events to manage complex processes for applications

Redux-saga is a middleware for Redux, and the purpose of middleware is to provide additional functionality for Redux.
All operations in reducers are synchronous and pure, that is, reducer are pure functions, pure functions:A function returns results that depend only on its arguments, and does not have external side effects during execution, that is, output what is passed to it.
But in real application development, we want to do something asynchronous and not pure, which is called in the functional programming specificationSide effects

2.`redux-saga`The working principle of

redux-sageusinggeneratorFunction toyield effects
generatorThe pause () function pauses execution and then resumes where it left off
effectIs a simple object that contains a number of methodsmiddlewareExplain execution information
Can be achieved byeffects apiSuch as:fork.call.take.put.cancelTo create such aseffect

3.`redux-sage`classification

worker saga Work with saga, such as calling apis, making asynchronous requests, and getting the results of asynchronous encapsulation
watcher sagaListen for the sent action when it is receivedactionOr when it knows it’s triggeredworkerPerform a task
root sagaImmediately startsagaThe only entrance to

4. Basic

├ ─ ─ components │ └ ─ ─ Counter. Js ├ ─ ─ index. The js └ ─ ─ store ├ ─ ─ action - types. Js ├ ─ ─ the actions │ └ ─ ─ Counter. Js ├ ─ ─ index. The js ├ ─ ─ Reducers │ ├ ─ ─ counter. Js │ └ ─ ─ index. The js └ ─ ─ sagas └ ─ ─ index, jsCopy the code

4.1. Project dependencies

npm install react-redux redux redux-sage -S
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4.2.`src/index.js`

import React from 'react';
import ReactDOM from 'react-dom';
import { Provider } from 'react-redux';
import store from './store';
import Counter from './components/Counter'

ReactDOM.render(<Provider store={store}>
    <Counter />
</Provider>.document.getElementById('root'));
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4.2.`components/Counter.js`

import React from 'react';
import { connect } from 'react-redux';
import actions from '.. /store/actions/counter'

class Counter extends React.Component {
    render() {
        return <div>
            <p>{this.props.num}</p>
            <button onClick={this.props.add}>add</button>
            <button onClick={this.props.asyncAdd}>async add</button>
        </div>}}const mapStateToProps = state= > state.counter;
export default connect(mapStateToProps, actions)(Counter);
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4.3.`store/index.js`

import { createStore, applyMiddleware } from 'redux';
import createSagaMiddleware from 'redux-saga';
import reducers from './reducers';
import rootSage from './sagas';

// Reference saga middleware
const sagaMiddleware = createSagaMiddleware();
// Apply saga middleware. Once this middleware is used, all subsequent store.dispatch points to the dispatch method provided by sagaMiddleware
const store = applyMiddleware(sagaMiddleware)(createStore)(reducers);
// Let root saga start executing
sagaMiddleware.run(rootSage);
export default store;
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4.4.`store/action-types.js`

const ADD='ADD';
const ASYNC_ADD='ASYNC_ADD';
export {
    ADD,
    ASYNC_ADD
}
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4.5.`actions/counter.js`

import * as types from '.. /action-types';

const actions = {
    add() {
        return { type: types.ADD };
    },
    asyncAdd() {
        return { type: types.ASYNC_ADD }; }}export default actions;
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4.6.`reducers/index.js`

import { combineReducers } from 'redux';
import counter from './counter';

export default combineReducers({
    counter
})
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4.7.`reducers/counter.js`

import * as types from '.. /action-types';

const initialState = { num: 0 }
function counter(state = initialState, action) {
    switch (action.type) {
        case types.ADD:
            return { num: state.num + 1 };
        default:
            returnstate; }}export default counter;
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4.8.`sagas/index.js`

import { take, put } from 'redux-saga/effects';
import * as types from '.. /action-types';

function* rootSaga() {
    for (let i = 0; i < 3; i++) {
      	// Wait for someone to send an ASYNC_ADD command to the repository, then continue executing it, or get stuck
      	//take waits only once
        yield take(types.ASYNC_ADD);
      	// Send an action to the warehouse to call store.dispatch({type: types.add})
        yield put({ type: types.ADD }); }}export default rootSaga;
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5. Put&take implementation

Story - sage ├ ─ ─ createChannel. Js ├ ─ ─ effectTypes. Js ├ ─ ─ effects. The js ├ ─ ─ index. The js └ ─ ─ runSaga. JsCopy the code

5.1.`index.js`

import runSaga from './runSaga';
import createChannel from "./createChannel";

/ * * * *@returns Returns a middleware */
function createSagaMiddleware() {
    const channel = createChannel();
    let boundRunSaga;
    function sagaMiddleware(middlewareApi) {//{getState,dispatch}
        const { getState, dispatch } = middlewareApi;
        // bind this to null and the first argument to runSaga to env={getState, dispatch, channel}
        boundRunSaga = runSaga.bind(null, { getState, dispatch, channel })
        return function (next) {// The next middleware dispatch method
            return function (action) {/ / action
                // The original dispatch method is implemented, which directly sends async_add to the repository and then to the reducer
                next(action);
                / / execution channel. The put
                channel.put(action)
            }
        }
    }
    sagaMiddleware.run = saga= > boundRunSaga(saga);
    return sagaMiddleware;
}
export default createSagaMiddleware;
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5.2.`createChannel.js`

function createChannel() {
    let currentTakers = [];// The current listener

    /** * start listening for an action *@param {*} ActionType actionType ASYNC_ADD *@param {*} Taker is the next * /
    function take(actionType, taker) {
        taker.actionType = actionType;
        taker.cancel = () = > {
            currentTakers = currentTakers.filter(item= >item ! == taker); } currentTakers.push(taker); }/** * Triggers the execution of functions in the Takers array, but configures the action type *@param {*} Action Action object {type:types.ASYNC_ADD} */
    function put(action) {
        currentTakers.forEach(taker= > {
            if (taker.actionType === action.type) {
                //take takes effect once by default
                taker.cancel();
                taker(action);/ / the next function}})}return { take, put };
}
export default createChannel;
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5.3.`effectTypes.js`

/** listen for specific actions */
export const TAKE = 'TAKE';

/** Send actions to the warehouse */
export const PUT = 'PUT';
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5.4.`effects.js`

import * as effecTypes from './effectTypes';

/ * * * *@param {*} actionType 
 * @returns The return value is a plain object, called the instruction object */
export function take(actionType) {
    return { type: effecTypes.TAKE, actionType };
}

export function put(action) {
    return { type: effecTypes.PUT, action }
}
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5.5.`runSaga.js`

import * as effectTypes from './effectTypes';
/** * How to execute or start saga *@param {*} evn { getState, dispatch, channel }
 * @param {*} Saga can be passed either as a generator or as an iterator */
function runSaga(evn, saga) {
    const { getState, dispatch, channel } = evn;
    // Get the iterator
    const it = saga();
    function next(value) {
        /** * effect={ type: effecTypes.TAKE, actionType=types.ASYNC_ADD } * effect= { type: effecTypes.PUT, action } */
        const { value: effect, done } = it.next(value);
        if(! done) {switch (effect.type) {
                case effectTypes.TAKE:// Wait for an ASYNC_ADD action to be sent to the warehouse
                    Channel.put (action) if ASYNC_ADD is dispatched to the repository
                    // It waits for the action to happen, and if it doesn't, it gets stuck
                    channel.take(effect.actionType, next);
                    break;
                case effectTypes.PUT://put this effect does not block the current saga execution and executes immediately after dispatch
                    dispatch(effect.action);
                    // Execute immediately after dispatching
                    next();
                    break
                default:
                    break;
            }
        }
    }
    next();
}
export default runSaga;
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6. Support outputs`iterator`

6.1.`saga/index.js`

import { take, put } from '.. /.. /redux-saga/effects';
import * as types from '.. /action-types';

+ function* add() {+// Send an action to the warehouse to call store.dispatch({type: types.add})
+   yield put({ type: types.ADD }); +}function* rootSaga() {
  for (let i = 0; i < 3; i++) {
    // Wait for someone to send an ASYNC_ADD command to the repository, then continue executing it, or get stuck
    //take waits only once
    yield take(types.ASYNC_ADD);
+    yieldadd(); }}Copy the code

6.2.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';

function runSaga(evn, saga) {
    const { getState, dispatch, channel } = evn;
    //saga can be either a generator or an iterator
+   const it = typeof saga === 'function' ? saga() : saga;
    function next(value) {
        const { value: effect, done } = it.next(value);
        if(! done) {// Effect may be an iterator yield add();
+           if (typeof effect[Symbol.iterator] === 'function') {
+               runSaga(evn, effect);
+               next();// Does not block current saga+}else {
                switch (effect.type) {
                    case effectTypes.TAKE:
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT:
                        dispatch(effect.action);
                        next();
                        break
                    default:
                        break;
                }
            }
        }
    }
    next();
}
export default runSaga;
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7. Support takeEvery

atakeIt’s like a process running in the background, based onredux-sagaYou can run more than one application at the same timetask
throughforkFunction to createtask

7.1.`saga/index.js`

+ import { take, put, takeEvery } from '.. /.. /redux-saga/effects';
  import * as types from '.. /action-types';

function* add() {
  // Send an action to the warehouse to call store.dispatch({type: types.add})
  yield put({ type: types.ADD });
}

function* rootSaga() {+yield takeEvery(types.ASYNC_ADD, add)
}

export default rootSaga;
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7.2.`redux-saga/effectTypes.js`

/** listen for specific actions */
export const TAKE = 'TAKE';

/** Send actions to the warehouse */
export const PUT = 'PUT';

  /** Starts a new child process, normally without blocking the current saga */
+ export const FORK = 'FORK';
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7.3.`redux-saga/effects.js`

import * as effecTypes from './effectTypes';


export function take(actionType) {
    return { type: effecTypes.TAKE, actionType };
}

export function put(action) {
    return { type: effecTypes.PUT, action }
}

/** * execute saga * as a new child process@param {*} saga 
 * @returns * /
+ export function fork(saga) {+return { type: effecTypes.FORK, saga }; +}/** * Waits for each actionType to be dispatched, and then a separate child calls saga to execute *@param {*} actionType 
 * @param {*} saga 
 * @returns * /
+ export function takeEvery(actionType, saga) {+function* takeEveryHelper() {+while (true) {// Write an infinite loop that executes each time
+           yield take(actionType);// Wait for an action type
+           yield fork(saga);// Start a new child process to execute saga+} +} +// start a new subprocess to takeEveryHelper
+   returnfork(takeEveryHelper); +}Copy the code

7.4.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';

function runSaga(env, saga) {
    const { getState, dispatch, channel } = env;
    const it = typeof saga === 'function' ? saga() : saga;
    function next(value) {
        const { value: effect, done } = it.next(value);
        if(! done) {if (typeof effect[Symbol.iterator] === 'function') {
                runSaga(env, effect);
                next();
            } else {
                switch (effect.type) {
                    case effectTypes.TAKE:
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT:
                        dispatch(effect.action);
                        next();
                        break;
+                   case effectTypes.FORK:// Start a new child process to execute saga
+                       runSaga(env, effect.saga);
+                       next();// Does not block current saga
+                       break;
                    default:
                        break;
                }
            }
        }
    }
    next();
}
export default runSaga;
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Support 8.`Promise`

8.1.`sagas/index.js`

import { take, put, takeEvery } from '.. /.. /redux-saga/effects';
import * as types from '.. /action-types';

+ const delay = ms= > new Promise((resolve) = >{+setTimeout(resolve, ms); +})function* add() {+yield delay(2000);
  // Send an action to the warehouse to call store.dispatch({type: types.add})
  yield put({ type: types.ADD });
}

function* rootSaga() {
  yield takeEvery(types.ASYNC_ADD, add)
}

export default rootSaga;
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8.2.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';

function runSaga(env, saga) {
    const { getState, dispatch, channel } = env;
    const it = typeof saga === 'function' ? saga() : saga;
    function next(value) {
        const { value: effect, done } = it.next(value);
        if(! done) {if (typeof effect[Symbol.iterator] === 'function') { runSaga(env, effect); next(); +}else if (typeof effect.then === 'function') {/ / support promise
+               effect.then(next);// blocks until the promise succeeds and next automatically goes+}else {
                switch (effect.type) {
                    case effectTypes.TAKE:
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT:
                        dispatch(effect.action);
                        next();
                        break;
                    case effectTypes.FORK:
                        runSaga(env, effect.saga);
                        next();
                        break;
                    default:
                        break;
                }
            }
        }
    }
    next();
}
export default runSaga;
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9. Support`all`

9.1.`sagas/index.js`

+ import { take, put, takeEvery, call } from '.. /.. /redux-saga/effects';
import * as types from '.. /action-types';

const delay = ms= > new Promise((resolve) = > {
  setTimeout(resolve, ms);
})

function* add() {+yield call(delay, 1000);
  yield put({ type: types.ADD });
}

function* rootSaga() {
  yield takeEvery(types.ASYNC_ADD, add)
}

export default rootSaga;
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9.2.`redux-saga/effectTypes.js`

/** listen for specific actions */
export const TAKE = 'TAKE';

/** Send actions to the warehouse */
export const PUT = 'PUT';

/** Starts a new child process, normally without blocking the current saga */
export const FORK = 'FORK';

+ /** Calls a function, which by default returns a Promise */
+ export const CALL='CALL';
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9.3.`redux-saga/effects.js`

import * as effecTypes from './effectTypes';

/ * * * *@param {*} actionType 
 * @returns The return value is a plain object, called the instruction object */
export function take(actionType) {
    return { type: effecTypes.TAKE, actionType };
}

export function put(action) {
    return { type: effecTypes.PUT, action }
}

/** * execute saga * as a new child process@param {*} saga 
 * @returns * /
export function fork(saga) {
    return { type: effecTypes.FORK, saga };
}

/** * Waits for each actionType to be dispatched, and then a separate child calls saga to execute *@param {*} actionType 
 * @param {*} saga 
 * @returns * /
export function takeEvery(actionType, saga) {
    function* takeEveryHelper() {
        while (true) {// Write an infinite loop that executes each time
            yield take(actionType);// Wait for an action type
            yield fork(saga);// Start a new child process to execute saga}}// start a new subprocess to takeEveryHelper
    return fork(takeEveryHelper);
}


+ export function call(fn, ... args) {+return { type: effecTypes.CALL, fn, args }
+ }
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9.4.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';

function runSaga(env, saga) {
    const { getState, dispatch, channel } = env;
    const it = typeof saga === 'function' ? saga() : saga;
    function next(value) {
        const { value: effect, done } = it.next(value);
        if(! done) {if (typeof effect[Symbol.iterator] === 'function') {
                runSaga(env, effect);
                next();
            } else if (typeof effect.then === 'function') {
                effect.then(next);
            } else {
                switch (effect.type) {
                    case effectTypes.TAKE:
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT:
                        dispatch(effect.action);
                        next();
                        break;
                    case effectTypes.FORK:
                        runSaga(env, effect.saga);
                        next();
                        break;
+                   caseeffectTypes.CALL: + effect.fn(... effect.args).then(next) +break;
                    default:
                        break;
                }
            }
        }
    }
    next();
}
export default runSaga;
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Support 10.`cps`

10.1.`sagas/index.js`

import { take, put, takeEvery, call, cps } from '.. /.. /redux-saga/effects';
import * as types from '.. /action-types';

+ const delay2 = (ms, callback) = >{+setTimeout(() = > {
    // The first argument is an error result
+    callback(null.'ok') + }, ms); +}function* add() {
  // Tell saga middleware to execute delay2 iteration with 1000
+  yield cps(delay2, 1000);
  
  yield put({ type: types.ADD });
}

function* rootSaga() {
  yield takeEvery(types.ASYNC_ADD, add)
}

export default rootSaga;
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10.2.`redux-saga/effectTypes.js`

/** listen for specific actions */
export const TAKE = 'TAKE';

/** Send actions to the warehouse */
export const PUT = 'PUT';

/** Starts a new child process, normally without blocking the current saga */
export const FORK = 'FORK';

/** Calls a function, which by default returns a Promise */
export const CALL = 'CALL';

	/** Call a function whose last argument should be a callback that allows saga to proceed */
+ export const CPS = 'CPS';
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10.3.`redux-saga/effects.js`

import * as effecTypes from './effectTypes';

/ * * * *@param {*} actionType 
 * @returns The return value is a plain object, called the instruction object */
export function take(actionType) {
    return { type: effecTypes.TAKE, actionType };
}

export function put(action) {
    return { type: effecTypes.PUT, action }
}

/** * execute saga * as a new child process@param {*} saga 
 * @returns * /
export function fork(saga) {
    return { type: effecTypes.FORK, saga };
}

/** * Waits for each actionType to be dispatched, and then a separate child calls saga to execute *@param {*} actionType 
 * @param {*} saga 
 * @returns * /
export function takeEvery(actionType, saga) {
    function* takeEveryHelper() {
        while (true) {// Write an infinite loop that executes each time
            yield take(actionType);// Wait for an action type
            yield fork(saga);// Start a new child process to execute saga}}// start a new subprocess to takeEveryHelper
    return fork(takeEveryHelper);
}


export function call(fn, ... args) {
    return { type: effecTypes.CALL, fn, args }
}

+ export function cps(fn, ... args) {+return { type: effecTypes.CPS, fn, args }; +}Copy the code

10.4.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';

function runSaga(env, saga) {
    const { getState, dispatch, channel } = env;
    const it = typeof saga === 'function' ? saga() : saga;
    function next(value, isError) {+let result;
+       if (isError) {
+           result = it.throw(value);// The iterator failed+}else{ + result = it.next(value); +},const { value: effect, done } = result;
        if(! done) {// Effect may be an iterator yield add();
            if (typeof effect[Symbol.iterator] === 'function') {
                runSaga(env, effect);
                next();// Does not block current saga
            } else if (typeof effect.then === 'function') {/ / support promise
                effect.then(next);// blocks until the promise succeeds and next automatically goes
            } else {
                switch (effect.type) {
                    case effectTypes.TAKE:// Wait for an ASYNC_ADD action to be sent to the warehouse
                        Channel.put (action) if ASYNC_ADD is dispatched to the repository
                        // It waits for the action to happen, and if it doesn't, it gets stuck
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT://put this effect does not block the current saga execution and executes immediately after dispatch
                        dispatch(effect.action);
                        // Execute immediately after dispatching
                        next();
                        break;
                    case effectTypes.FORK:// Start a new child process to execute saga
                        runSaga(env, effect.saga);
                        next();// Does not block current saga
                        break;
                    caseeffectTypes.CALL: effect.fn(... effect.args).then(next)break;
+                   caseeffectTypes.CPS: + effect.fn(... effect.args,(err, data) = >{+if (err) {// If err is not null, there is an error. The first argument to next is an error object
+                               next(err, true); +}else{ + next(data); +} +}) +break;
                    default:
                        break;
                }
            }
        }
    }
    next();
}
export default runSaga;
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11. Support`all`

11.1.`sagas/index.js`

+ import { take, put, takeEvery, call, cps, all } from '.. /.. /redux-saga/effects';
import * as types from '.. /action-types';

+ function* add1() {+for (let i = 0; i < 3; i++) {
+    yield take(types.ASYNC_ADD);
+    yield put({ type: types.ADD })
+  }
+  return 'add1'; +},function* add2() {+for (let i = 0; i < 2; i++) {
+    yield take(types.ASYNC_ADD);
+    yield put({ type: types.ADD })
+  }
+  return 'add2'; +}function* rootSaga() {+yield all([add1, add2]);
+  console.log(result)//=>['add1','add2']  
}

export default rootSaga;
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11.2.`redux-saga/effectTypes.js`

/** listen for specific actions */
export const TAKE = 'TAKE';

/** Send actions to the warehouse */
export const PUT = 'PUT';

/** Starts a new child process, normally without blocking the current saga */
export const FORK = 'FORK';

/** Calls a function, which by default returns a Promise */
export const CALL = 'CALL';

/** Call a function whose last argument should be a callback that allows saga to proceed */
export const CPS = 'CPS';

+ /** Receive multiple iterators until all iterators are finished */
+ export const ALL = 'ALL';
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11.3.`redux-saga/effects.js`

import * as effecTypes from './effectTypes';

/ * * * *@param {*} actionType 
 * @returns The return value is a plain object, called the instruction object */
export function take(actionType) {
    return { type: effecTypes.TAKE, actionType };
}

export function put(action) {
    return { type: effecTypes.PUT, action }
}

/** * execute saga * as a new child process@param {*} saga 
 * @returns * /
export function fork(saga) {
    return { type: effecTypes.FORK, saga };
}

/** * Waits for each actionType to be dispatched, and then a separate child calls saga to execute *@param {*} actionType 
 * @param {*} saga 
 * @returns * /
export function takeEvery(actionType, saga) {
    function* takeEveryHelper() {
        while (true) {// Write an infinite loop that executes each time
            yield take(actionType);// Wait for an action type
            yield fork(saga);// Start a new child process to execute saga}}// start a new subprocess to takeEveryHelper
    return fork(takeEveryHelper);
}


export function call(fn, ... args) {
    return { type: effecTypes.CALL, fn, args }
}

export function cps(fn, ... args) {
    return { type: effecTypes.CPS, fn, args };
}

+ export function all(effects) {+return { type: effecTypes.ALL, effects }; +}Copy the code

11.4.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';

+ function runSaga(env, saga, callbackDone) {
    const { getState, dispatch, channel } = env;
    //saga can be either a generator or an iterator
    const it = typeof saga === 'function' ? saga() : saga;
    function next(value, isError) {
        let result;
        if (isError) {
            result = it.throw(value);// The iterator failed
        } else {
            result = it.next(value);
        }
        const { value: effect, done } = result;
        if(! done) {// Effect may be an iterator yield add();
            if (typeof effect[Symbol.iterator] === 'function') {
                runSaga(env, effect);
                next();// Does not block current saga
            } else if (typeof effect.then === 'function') {/ / support promise
                effect.then(next);// blocks until the promise succeeds and next automatically goes
            } else {
                switch (effect.type) {
                    case effectTypes.TAKE:
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT:
                        dispatch(effect.action);
                        // Execute immediately after dispatching
                        next();
                        break;
                    case effectTypes.FORK:// Start a new child process to execute saga
                        runSaga(env, effect.saga);
                        next();// Does not block current saga
                        break;
                    caseeffectTypes.CALL: effect.fn(... effect.args).then(next)break;
                    caseeffectTypes.CPS: effect.fn(... effect.args,(err, data) = > {
                            if (err) {// If err is not null, there is an error. The first argument to next is an error object
                                next(err, true);
                            } else{ next(data); }})break;
+                   case effectTypes.ALL:
+                       let effects = effect.effects;
+                       const result = [];
+                       let completedCount = 0;
+                       effects.forEach((effect, index) = > {
+                           runSaga(env, effect, (res) = > {
+                               result[index] = res;
+                               // Determine whether the number of completions is equal to the total number
+                               if (++completedCount === effects.length) {
+                                   next(result);// The current saga can continue+} +}) +}) +break;
                    default:
                        break; +}}}else {
+           callbackDone && callbackDone(effect);
+       }
    }
    next();
}
export default runSaga;
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Support 12.`cancel`

12.1.`components/Counter.js`

import React from 'react';
import { connect } from 'react-redux';
import actions from '.. /store/actions/counter'

class Counter extends React.Component {
    render() {
        return <div>
            <p>{this.props.num}</p>
            <button onClick={this.props.add}>add</button>
            <button onClick={this.props.asyncAdd}>async add</button>
+           <button onClick={this.props.stop}>stop</button>
        </div>}}const mapStateToProps = state= > state.counter;
export default connect(mapStateToProps, actions)(Counter);
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12.2.`store/action-types.js`

	const ADD='ADD';
	const ASYNC_ADD='ASYNC_ADD';
+ const STOP_ADD='STOP_ADD';
export {
    ADD,
    ASYNC_ADD,
+   STOP_ADD
}
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12.3.`actions/counter.js`

import * as types from '.. /action-types';

const actions = {
    add() {
        return { type: types.ADD };
    },
    asyncAdd() {
        return { type: types.ASYNC_ADD };
    },
+   stop(){+return { type: types.STOP_ADD }; +}}export default actions;
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12.4.`sagas/index.js`

+ import { take, put, takeEvery, call, cps, all, delay, fork, cancel } from '.. /.. /redux-saga/effects';
  import * as types from '.. /action-types';

+ function* add() {+while (true) {+yield delay(1000);
+    yield put({ type: types.ADD }); + +}}function* rootSaga() {+const task = yield fork(add);
+  yield take(types.STOP_ADD);
+  yield cancel(task);
}

export default rootSaga;
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12.5.`redux-saga/effectTypes.js`

/** listen for specific actions */
export const TAKE = 'TAKE';

/** Send actions to the warehouse */
export const PUT = 'PUT';

/** Starts a new child process, normally without blocking the current saga */
export const FORK = 'FORK';

/** Calls a function, which by default returns a Promise */
export const CALL = 'CALL';

/** Call a function whose last argument should be a callback that allows saga to proceed */
export const CPS = 'CPS';

/** Receive multiple iterators until all iterators are finished */
export const ALL = 'ALL';

+ /** Cancel a task */
+ export const CANCEL='CANCEL';
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12.6.`redux-saga/`

import * as effecTypes from './effectTypes';

/ * * * *@param {*} actionType 
 * @returns The return value is a plain object, called the instruction object */
export function take(actionType) {
    return { type: effecTypes.TAKE, actionType };
}

export function put(action) {
    return { type: effecTypes.PUT, action }
}

/** * execute saga * as a new child process@param {*} saga 
 * @returns * /
export function fork(saga) {
    return { type: effecTypes.FORK, saga };
}

/** * Waits for each actionType to be dispatched, and then a separate child calls saga to execute *@param {*} actionType 
 * @param {*} saga 
 * @returns * /
export function takeEvery(actionType, saga) {
    function* takeEveryHelper() {
        while (true) {// Write an infinite loop that executes each time
            yield take(actionType);// Wait for an action type
            yield fork(saga);// Start a new child process to execute saga}}// start a new subprocess to takeEveryHelper
    return fork(takeEveryHelper);
}


export function call(fn, ... args) {
    return { type: effecTypes.CALL, fn, args }
}

export function cps(fn, ... args) {
    return { type: effecTypes.CPS, fn, args };
}

export function all(effects) {
    return { type: effecTypes.ALL, effects };
}

+ export function cancel(task) {+return { type: effecTypes.CANCEL, task }; +},function delayP(ms) {+const promise = new Promise(resolve= >{+setTimeout(resolve, ms); +}); +returnpromise; +},export const delay = call.bind(null, delayP);
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12.7.`redux-saga/symbols.js`

export const TASK_CANCEL=Symbol('TASK_CANCEL');
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12.8.`redux-saga/runSaga.js`

import * as effectTypes from './effectTypes';
+ import { TASK_CANCEL } from './symbols';

function runSaga(env, saga, callbackDone) {
    // Every time runSaga is executed, a task object is created for it
+   const task = { cancel: () = > next(TASK_CANCEL) };
    const { getState, dispatch, channel } = env;
    const it = typeof saga === 'function' ? saga() : saga;
    function next(value, isError) {
        let result;
        if(isError) { result = it.throw(value); +}else if (value === TASK_CANCEL) {// If next=TASK_CANCEL, we cancel the current task
+           result = it.return(value);//it.return() to end the current saga+}else {
            result = it.next(value);
        }
        const { value: effect, done } = result;
        if(! done) {if (typeof effect[Symbol.iterator] === 'function') {
                runSaga(env, effect);
                next();
            } else if (typeof effect.then === 'function') {
                effect.then(next);
            } else {
                switch (effect.type) {
                    case effectTypes.TAKE:
                        channel.take(effect.actionType, next);
                        break;
                    case effectTypes.PUT:
                        dispatch(effect.action);
                        // Execute immediately after dispatching
                        next();
                        break;
                    case effectTypes.FORK:// Start a new child process to execute saga
+                       const forkTask = runSaga(env, effect.saga);Return a task
+                       next(forkTask);// Does not block current saga
                        break;
                    caseeffectTypes.CALL: effect.fn(... effect.args).then(next)break;
                    caseeffectTypes.CPS: effect.fn(... effect.args,(err, data) = > {
                            if (err) {// If err is not null, there is an error. The first argument to next is an error object
                                next(err, true);
                            } else{ next(data); }})break;
                    case effectTypes.ALL:
                        let effects = effect.effects;
                        const result = [];
                        let completedCount = 0;
                        effects.forEach((effect, index) = > {
                            runSaga(env, effect, (res) = > {
                                result[index] = res;
                                // Determine whether the number of completions is equal to the total number
                                if (++completedCount === effects.length) {
                                    next(result);// The current saga can continue}})})break;
+                   case effectTypes.CANCEL:
+                       effect.task.cancel();// Call task's cancel method ->next(TASK_CANCEL) to cancel the task
+                       next();// The current saga continues without blocking
+                       break;
                    default:
                        break; }}}else {
            callbackDone && callbackDone(effect);
        }
    }
    next();
+   return task;
}
export default runSaga;
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Redux-saga source code analysis

Redux-saga source code analysis

1. Whyredux-saga

2.redux-sagaThe working principle of

3.redux-sageclassification

4. Basic

4.1. Project dependencies

4.2.src/index.js

4.2.components/Counter.js

4.3.store/index.js

4.4.store/action-types.js

4.5.actions/counter.js

4.6.reducers/index.js

4.7.reducers/counter.js

4.8.sagas/index.js

5. Put&take implementation

5.1.index.js

5.2.createChannel.js

5.3.effectTypes.js

5.4.effects.js

5.5.runSaga.js

6. Support outputsiterator

6.1.saga/index.js

6.2.redux-saga/runSaga.js

7. Support takeEvery

7.1.saga/index.js

7.2.redux-saga/effectTypes.js

7.3.redux-saga/effects.js

7.4.redux-saga/runSaga.js

Support 8.Promise

8.1.sagas/index.js

8.2.redux-saga/runSaga.js

9. Supportall

9.1.sagas/index.js

9.2.redux-saga/effectTypes.js

9.3.redux-saga/effects.js

9.4.redux-saga/runSaga.js

Support 10.cps

10.1.sagas/index.js

10.2.redux-saga/effectTypes.js

10.3.redux-saga/effects.js

10.4.redux-saga/runSaga.js

11. Supportall

11.1.sagas/index.js

11.2.redux-saga/effectTypes.js

11.3.redux-saga/effects.js

11.4.redux-saga/runSaga.js

Support 12.cancel

12.1.components/Counter.js

12.2.store/action-types.js

12.3.actions/counter.js

12.4.sagas/index.js

12.5.redux-saga/effectTypes.js

12.6.redux-saga/

12.7.redux-saga/symbols.js

12.8.redux-saga/runSaga.js

Related Posts

Basic usage of Node.js

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1. Why`redux-saga`

2.`redux-saga`The working principle of

3.`redux-sage`classification

4.2.`src/index.js`

4.2.`components/Counter.js`

4.3.`store/index.js`

4.4.`store/action-types.js`

4.5.`actions/counter.js`

4.6.`reducers/index.js`

4.7.`reducers/counter.js`

4.8.`sagas/index.js`

5.1.`index.js`

5.2.`createChannel.js`

5.3.`effectTypes.js`

5.4.`effects.js`

5.5.`runSaga.js`

6. Support outputs`iterator`

6.1.`saga/index.js`

6.2.`redux-saga/runSaga.js`

7.1.`saga/index.js`

7.2.`redux-saga/effectTypes.js`

7.3.`redux-saga/effects.js`

7.4.`redux-saga/runSaga.js`

Support 8.`Promise`

8.1.`sagas/index.js`

8.2.`redux-saga/runSaga.js`

9. Support`all`

9.1.`sagas/index.js`

9.2.`redux-saga/effectTypes.js`

9.3.`redux-saga/effects.js`

9.4.`redux-saga/runSaga.js`

Support 10.`cps`

10.1.`sagas/index.js`

10.2.`redux-saga/effectTypes.js`

10.3.`redux-saga/effects.js`

10.4.`redux-saga/runSaga.js`

11. Support`all`

11.1.`sagas/index.js`

11.2.`redux-saga/effectTypes.js`

11.3.`redux-saga/effects.js`

11.4.`redux-saga/runSaga.js`

Support 12.`cancel`

12.1.`components/Counter.js`

12.2.`store/action-types.js`

12.3.`actions/counter.js`

12.4.`sagas/index.js`

12.5.`redux-saga/effectTypes.js`

12.6.`redux-saga/`

12.7.`redux-saga/symbols.js`

12.8.`redux-saga/runSaga.js`