javascript - 在React/Flux中处理计时器

Question

我正在开发一个应用程序，在该应用程序中，我希望计时器从60秒倒计时到0，然后更改一些内容，然后计时器在60再次重启。

我已经在React和Flux中实现了它，但是由于我是新手，所以我仍然遇到一些问题。

我现在想为计时器添加一个开始/停止按钮。我不确定在哪里放置/处理计时器状态。

我有一个组件Timer.jsx，看起来像这样:

var React = require('react');
var AppStore = require('../stores/app-store.js');
var AppActions = require('../actions/app-actions.js');

function getTimeLeft() {
  return {
    timeLeft: AppStore.getTimeLeft()
  }
}

var Timer = React.createClass({
  _tick: function() {
    this.setState({ timeLeft: this.state.timeLeft - 1 });
    if (this.state.timeLeft < 0) {
      AppActions.changePattern();
      clearInterval(this.interval);
    }
  },
  _onChange: function() {
    this.setState(getTimeLeft());
    this.interval = setInterval(this._tick, 1000);
  },
  getInitialState: function() {
    return getTimeLeft();
  },
  componentWillMount: function() {
    AppStore.addChangeListener(this._onChange);
  },
  componentWillUnmount: function() {
    clearInterval(this.interval);
  },
  componentDidMount: function() {
    this.interval = setInterval(this._tick, 1000);
  },
  render: function() {
    return (
      <small>
        ({ this.state.timeLeft })
      </small>
    )
  }
});

module.exports = Timer;

它从商店那里获取倒计时持续时间，我在那里:
var _timeLeft = 60;
现在，当我想实现启动/停止按钮时，我觉得我也应该通过Flux Actions来实现，对吗？所以我想在我的商店里放这样的东西:

dispatcherIndex: AppDispatcher.register(function(payload) {
  var action = payload.action;

  switch(action.actionType) {
    case AppConstants.START_TIMER:
      // do something
      break;
    case AppConstants.STOP_TIMER:
      // do something
      break;
    case AppConstants.CHANGE_PATTERN:
      _setPattern();
      break;
  }

  AppStore.emitChange();

  return true;
})

但是，由于我的Timer组件当前正在处理setInterval，所以我不知道如何使我的START / STOP_TIMER事件正常工作。我应该将setInterval内容从Timer组件移到Store并以某种方式传递给我的组件吗？

完整代码可以在here中找到。

Answer 1

我最终下载了您的代码并实现了所需的启动/停止/重置功能。我认为这可能是解释问题的最佳方法-显示可以运行和测试的代码以及一些注释。

实际上，我最终得到了两种实现。我将它们称为实现A和实现B。

我认为展示这两种实现会很有趣。希望它不会引起太多困惑。

记录下来，实现A是更好的版本。

以下是这两种实现的简要说明:

实现A

此版本在App组件级别跟踪状态。通过将props传递到Timer组件来管理计时器。计时器组件确实会跟踪自己的剩余时间状态。

实现B

此版本使用TimerStore和TimerAction模块来管理组件的状态和事件，从而在Timer组件级别跟踪计时器状态。

实现B的最大(可能是致命的)缺点是您只能拥有一个Timer组件。这是由于TimerStore和TimerAction模块本质上是Singletons。

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实现A

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此版本在App组件级别跟踪状态。这里的大多数注释都在该版本的代码中。

通过将props传递给计时器来管理计时器。

此实现的代码更改 list :

app-constants.js

app-actions.js

app-store.js

App.jsx

Timer.jsx

app-constants.js

在这里，我只是添加了一个用于重置计时器的常量。

module.exports = {
  START_TIMER: 'START_TIMER',
  STOP_TIMER: 'STOP_TIMER',
  RESET_TIMER: 'RESET_TIMER',
  CHANGE_PATTERN: 'CHANGE_PATTERN'
};

app-actions.js

我刚刚添加了一个调度方法来处理重置计时器操作。

var AppConstants = require('../constants/app-constants.js');
var AppDispatcher = require('../dispatchers/app-dispatcher.js');

var AppActions = {
  changePattern: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.CHANGE_PATTERN
    })
  },
  resetTimer: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.RESET_TIMER
    })
  },
  startTimer: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.START_TIMER
    })
  },
  stopTimer: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.STOP_TIMER
    })
  }
};

module.exports = AppActions;

app-store.js

这是情况有所改变的地方。我在进行更改的地方添加了详细的注释。

var AppDispatcher = require('../dispatchers/app-dispatcher.js');
var AppConstants = require('../constants/app-constants.js');
var EventEmitter = require('events').EventEmitter;
var merge = require('react/lib/Object.assign');


// I added a TimerStatus model (probably could go in its own file)
// to manage whether the timer is "start/stop/reset".
//
// The reason for this is that reset state was tricky to handle since the Timer
// component no longer has access to the "AppStore". I'll explain the reasoning for
// that later.
//
// To solve that problem, I added a `reset` method to ensure the state
// didn't continuously loop "reset". This is probably not very "Flux".
//
// Maybe a more "Flux" alternative is to use a separate TimerStore and
// TimerAction? 
//
// You definitely don't want to put them in AppStore and AppAction
// to make your timer component more reusable.
//
var TimerStatus = function(status) {
  this.status = status;
};

TimerStatus.prototype.isStart = function() {
  return this.status === 'start';
};

TimerStatus.prototype.isStop = function() {
  return this.status === 'stop';
};

TimerStatus.prototype.isReset = function() {
  return this.status === 'reset';
};

TimerStatus.prototype.reset = function() {
  if (this.isReset()) {
    this.status = 'start';
  }
};


var CHANGE_EVENT = "change";

var shapes = ['C', 'A', 'G', 'E', 'D'];
var rootNotes = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#'];

var boxShapes = require('../data/boxShapes.json');


// Added a variable to keep track of timer state. Note that this state is
// managed by the *App Component*.
var _timerStatus = new TimerStatus('start');


var _pattern = _setPattern();

function _setPattern() {
  var rootNote = _getRootNote();
  var shape = _getShape();
  var boxShape = _getBoxForShape(shape);

  _pattern = {
    rootNote: rootNote,
    shape: shape,
    boxShape: boxShape
  };

  return _pattern;
}

function _getRootNote() {
  return rootNotes[Math.floor(Math.random() * rootNotes.length)];
}

function _getShape() {
  return shapes[Math.floor(Math.random() * shapes.length)];
}

function _getBoxForShape(shape) {
  return boxShapes[shape];
}


// Simple function that creates a new instance of TimerStatus set to "reset"
function _resetTimer() {
  _timerStatus = new TimerStatus('reset');
}

// Simple function that creates a new instance of TimerStatus set to "stop"
function _stopTimer() {
  _timerStatus = new TimerStatus('stop');
}

// Simple function that creates a new instance of TimerStatus set to "start"
function _startTimer() {
  _timerStatus = new TimerStatus('start');
}


var AppStore = merge(EventEmitter.prototype, {
  emitChange: function() {
    this.emit(CHANGE_EVENT);
  },

  addChangeListener: function(callback) {
    this.on(CHANGE_EVENT, callback);
  },

  removeChangeListener: function(callback) {
    this.removeListener(CHANGE_EVENT, callback);
  },


  // Added this function to get timer status from App Store
  getTimerStatus: function() {
    return _timerStatus;
  },


  getPattern: function() {
    return _pattern;
  },

  dispatcherIndex: AppDispatcher.register(function(payload) {
    var action = payload.action;

    switch(action.actionType) {
      case AppConstants.RESET_TIMER:
        // Handle reset action
        _resetTimer();
        break;
      case AppConstants.START_TIMER:
        // Handle start action
        _startTimer();
        break;
      case AppConstants.STOP_TIMER:
        // Handle stop action
        _stopTimer();
        break;
      case AppConstants.CHANGE_PATTERN:
        _setPattern();
        break;
    }

    AppStore.emitChange();

    return true;
  })
});

module.exports = AppStore;

App.jsx

App.jsx中有许多更改，特别是我们已将状态从计时器组件移至App组件。再次在代码中详细注释。

var React = require('react');

var Headline = require('./components/Headline.jsx');
var Scale = require('./components/Scale.jsx');
var RootNote = require('./components/RootNote.jsx');
var Shape = require('./components/Shape.jsx');
var Timer = require('./components/Timer.jsx');


// Removed AppActions and AppStore from Timer component and moved
// to App component. This is done to to make the Timer component more
// reusable.
var AppActions = require('./actions/app-actions.js');
var AppStore = require('./stores/app-store.js');


// Use the AppStore to get the timerStatus state
function getAppState() {
  return {
    timerStatus: AppStore.getTimerStatus()
  }
}

var App = React.createClass({
  getInitialState: function() {
    return getAppState();
  },


  // Listen for change events in AppStore
  componentDidMount: function() {
    AppStore.addChangeListener(this.handleChange);
  },


  // Stop listening for change events in AppStore
  componentWillUnmount: function() {
    AppStore.removeChangeListener(this.handleChange);
  },


  // Timer component has status, defaultTimeout attributes.
  // Timer component has an onTimeout event (used for changing pattern)
  // Add three basic buttons for Start/Stop/Reset
  render: function() {
    return (
      <div>
        <header>
          <Headline />
          <Scale />
        </header>
        <section>
          <RootNote />
          <Shape />
          <Timer status={this.state.timerStatus} defaultTimeout="15" onTimeout={this.handleTimeout} />
          <button onClick={this.handleClickStart}>Start</button>
          <button onClick={this.handleClickStop}>Stop</button>
          <button onClick={this.handleClickReset}>Reset</button>
        </section>
      </div>
    );
  },


  // Handle change event from AppStore
  handleChange: function() {
    this.setState(getAppState());
  },


  // Handle timeout event from Timer component
  // This is the signal to change the pattern.
  handleTimeout: function() {
    AppActions.changePattern();
  },


  // Dispatch respective start/stop/reset actions
  handleClickStart: function() {
    AppActions.startTimer();
  },
  handleClickStop: function() {
    AppActions.stopTimer();
  },
  handleClickReset: function() {
    AppActions.resetTimer();
  }
});

module.exports = App;

Timer.jsx

自从我删除了Timer和AppStore依赖项以使AppActions组件更可重用以来，Timer也进行了许多更改。详细注释在代码中。

var React = require('react');


// Add a default timeout if defaultTimeout attribute is not specified.
var DEFAULT_TIMEOUT = 60;

var Timer = React.createClass({

  // Normally, shouldn't use props to set state, however it is OK when we
  // are not trying to synchronize state/props. Here we just want to provide an option to specify
  // a default timeout.
  //
  // See http://facebook.github.io/react/tips/props-in-getInitialState-as-anti-pattern.html)
  getInitialState: function() {
    this.defaultTimeout = this.props.defaultTimeout || DEFAULT_TIMEOUT;
    return {
      timeLeft: this.defaultTimeout
    };
  },


  // Changed this to `clearTimeout` instead of `clearInterval` since I used `setTimeout`
  // in my implementation
  componentWillUnmount: function() {
    clearTimeout(this.interval);
  },

  // If component updates (should occur when setState triggered on Timer component
  // and when App component is updated/re-rendered)
  //
  // When the App component updates we handle two cases:
  // - Timer start status when Timer is stopped
  // - Timer reset status. In this case, we execute the reset method of the TimerStatus
  //   object to set the internal status to "start". This is to avoid an infinite loop
  //   on the reset case in componentDidUpdate. Kind of a hack...
  componentDidUpdate: function() {
    if (this.props.status.isStart() && this.interval === undefined) {
      this._tick();
    } else if (this.props.status.isReset()) {
      this.props.status.reset();
      this.setState({timeLeft: this.defaultTimeout});
    }
  },

  // On mount start ticking
  componentDidMount: function() {
    this._tick();
  },


  // Tick event uses setTimeout. I find it easier to manage than setInterval.
  // We just keep calling setTimeout over and over unless the timer status is
  // "stop".
  //
  // Note that the Timer states is handled here without a store. You could probably
  // say this against the rules of "Flux". But for this component, it just seems unnecessary
  // to create separate TimerStore and TimerAction modules.
  _tick: function() {
    var self = this;
    this.interval = setTimeout(function() {
      if (self.props.status.isStop()) {
        self.interval = undefined;
        return;
      }
      self.setState({timeLeft: self.state.timeLeft - 1});
      if (self.state.timeLeft <= 0) {
        self.setState({timeLeft: self.defaultTimeout});
        self.handleTimeout();
      }
      self._tick();
    }, 1000);
  },

  // If timeout event handler passed to Timer component,
  // then trigger callback.
  handleTimeout: function() {
    if (this.props.onTimeout) {
      this.props.onTimeout();
    }
  }
  render: function() {
    return (
      <small className="timer">
        ({ this.state.timeLeft })
      </small>
    )
  },
});

module.exports = Timer;

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实现B

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代码更改 list :

app-constants.js

timer-actions.js(新)

timer-store.js(新)

app-store.js

App.jsx

Timer.jsx

app-constants.js

因为它们处理Timer组件，所以它们可能应该放在一个名为timer-constants.js的文件中。

module.exports = {
  START_TIMER: 'START_TIMER',
  STOP_TIMER: 'STOP_TIMER',
  RESET_TIMER: 'RESET_TIMER',
  TIMEOUT: 'TIMEOUT',
  TICK: 'TICK'
};

timer-actions.js

该模块是不言自明的。我添加了三个事件-超时，滴答和重置。有关详细信息，请参见代码。

var AppConstants = require('../constants/app-constants.js');
var AppDispatcher = require('../dispatchers/app-dispatcher.js');

module.exports = {

  // This event signals when the timer expires.
  // We can use this to change the pattern.
  timeout: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.TIMEOUT
    })
  },

  // This event decrements the time left
  tick: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.TICK
    })
  },

  // This event sets the timer state to "start"
  start: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.START_TIMER
    })
  },

  // This event sets the timer state to "stop"
  stop: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.STOP_TIMER
    })
  },

  // This event resets the time left and sets the state to "start"
  reset: function() {
    AppDispatcher.handleViewAction({
      actionType: AppConstants.RESET_TIMER
    })
  },
};

timer-store.js

我从AppStore中分离出了计时器内容。这是为了使Timer组件更具可重用性。

计时器存储区跟踪以下状态:

计时器状态-可以“开始”或“停止”

剩余时间-计时器

剩余时间

计时器存储处理以下事件:

计时器启动事件将计时器状态设置为启动。

计时器停止事件将计时器状态设置为停止。

节拍事件将剩余的时间减少1

计时器重置事件将剩余时间设置为默认时间，并将计时器状态设置为启动

这是代码:

var AppDispatcher = require('../dispatchers/app-dispatcher.js');
var AppConstants = require('../constants/app-constants.js');
var EventEmitter = require('events').EventEmitter;
var merge = require('react/lib/Object.assign');

var CHANGE_EVENT = "change";
var TIMEOUT_SECONDS = 15;

var _timerStatus = 'start';
var _timeLeft = TIMEOUT_SECONDS;

function _resetTimer() {
  _timerStatus = 'start';
  _timeLeft = TIMEOUT_SECONDS;
}

function _stopTimer() {
  _timerStatus = 'stop';
}

function _startTimer() {
  _timerStatus = 'start';
}

function _decrementTimer() {
  _timeLeft -= 1;
}

var TimerStore = merge(EventEmitter.prototype, {
  emitChange: function() {
    this.emit(CHANGE_EVENT);
  },

  addChangeListener: function(callback) {
    this.on(CHANGE_EVENT, callback);
  },

  removeChangeListener: function(callback) {
    this.removeListener(CHANGE_EVENT, callback);
  },

  getTimeLeft: function() {
    return _timeLeft;
  },

  getStatus: function() {
    return _timerStatus;
  },

  dispatcherIndex: AppDispatcher.register(function(payload) {
    var action = payload.action;

    switch(action.actionType) {
      case AppConstants.START_TIMER:
        _startTimer();
        break;
      case AppConstants.STOP_TIMER:
        _stopTimer();
        break;
      case AppConstants.RESET_TIMER:
        _resetTimer();
        break;
      case AppConstants.TIMEOUT:
        _resetTimer();
        break;
      case AppConstants.TICK:
        _decrementTimer();
        break;
    }

    TimerStore.emitChange();

    return true;
  })
});

module.exports = TimerStore;

app-store.js

可以将其命名为pattern-store.js，尽管您需要进行一些更改以使其可重用。具体来说，我直接在监听Timer的TIMEOUT Action /事件以触发模式更改。如果要重用模式更改，则可能不希望依赖。例如，如果您想通过单击按钮或其他方式来更改图案。

除此之外，我刚刚从AppStore中删除了所有与Timer相关的功能。

var AppDispatcher = require('../dispatchers/app-dispatcher.js');
var AppConstants = require('../constants/app-constants.js');
var EventEmitter = require('events').EventEmitter;
var merge = require('react/lib/Object.assign');

var CHANGE_EVENT = "change";

var shapes = ['C', 'A', 'G', 'E', 'D'];
var rootNotes = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#'];

var boxShapes = require('../data/boxShapes.json');

var _pattern = _setPattern();

function _setPattern() {
  var rootNote = _getRootNote();
  var shape = _getShape();
  var boxShape = _getBoxForShape(shape);

  _pattern = {
    rootNote: rootNote,
    shape: shape,
    boxShape: boxShape
  };

  return _pattern;
}

function _getRootNote() {
  return rootNotes[Math.floor(Math.random() * rootNotes.length)];
}

function _getShape() {
  return shapes[Math.floor(Math.random() * shapes.length)];
}

function _getBoxForShape(shape) {
  return boxShapes[shape];
}

var AppStore = merge(EventEmitter.prototype, {
  emitChange: function() {
    this.emit(CHANGE_EVENT);
  },

  addChangeListener: function(callback) {
    this.on(CHANGE_EVENT, callback);
  },

  removeChangeListener: function(callback) {
    this.removeListener(CHANGE_EVENT, callback);
  },

  getPattern: function() {
    return _pattern;
  },

  dispatcherIndex: AppDispatcher.register(function(payload) {
    var action = payload.action;

    switch(action.actionType) {
      case AppConstants.TIMEOUT:
        _setPattern();
        break;
    }

    AppStore.emitChange();

    return true;
  })
});

module.exports = AppStore;

App.jsx

在这里，我只添加了一些用于开始/停止/重置的按钮。单击时，将调度TimerAction。因此，如果您单击“停止”按钮，我们称为TimerAction.stop()

var React = require('react');

var Headline = require('./components/Headline.jsx');
var Scale = require('./components/Scale.jsx');
var RootNote = require('./components/RootNote.jsx');
var Shape = require('./components/Shape.jsx');
var Timer = require('./components/Timer.jsx');
var TimerActions = require('./actions/timer-actions.js');


var App = React.createClass({
  render: function() {
    return (
      <div>
        <header>
          <Headline />
          <Scale />
        </header>
        <section>
          <RootNote />
          <Shape />
          <Timer />
          <button onClick={this.handleClickStart}>Start</button>
          <button onClick={this.handleClickStop}>Stop</button>
          <button onClick={this.handleClickReset}>Reset</button>
        </section>
      </div>
    );
  },
  handleClickStart: function() {
    TimerActions.start();
  },
  handleClickStop: function() {
    TimerActions.stop();
  },
  handleClickReset: function() {
    TimerActions.reset();
  }
});

module.exports = App;

Timer.jsx

主要变化之一是我们使用的是TimerAction和TimerStore而不是最初使用的AppAction和AppStore。原因是尝试使Timer组件更具可重用性。

计时器具有以下状态:

状态计时器状态可以是“开始”或“停止”

时间左计时器

剩余时间

请注意，我使用了setTimeout而不是setInterval。我发现setTimeout更易于管理。

大部分逻辑都在_tick方法中。基本上，只要状态为“开始”，我们就继续调用setTimeout。

当计时器达到零时，我们发出timeout事件的信号。 TimerStore和AppStore正在侦听此事件。

TimerStore只会重置计时器。相同的重置事件。

AppStore将更改模式。

如果计时器未达到零，我们通过发信号“滴答”事件减去一秒钟。

最后，我们需要处理计时器停止然后再启动的情况。这可以通过componentDidUpdate钩子(Hook)来处理。当组件的状态更改或父组件被重新渲染时，将调用此挂钩。

在componentDidUpdate方法中，只有在状态为“开始”且未定义超时标识符的情况下，我们才确保启动“计时”。我们不希望运行多个setTimeouts。

var React = require('react');

var TimerActions = require('../actions/timer-actions.js');
var TimerStore = require('../stores/timer-store.js');

function getTimerState() {
  return {
    status: TimerStore.getStatus(),
    timeLeft: TimerStore.getTimeLeft()
  }
}

var Timer = React.createClass({
  _tick: function() {
    var self = this;
    this.interval = setTimeout(function() {
      if (self.state.status === 'stop') {
        self.interval = undefined;
        return;
      }

      if (self.state.timeLeft <= 0) {
        TimerActions.timeout();
      } else {
        TimerActions.tick();
      }
      self._tick();
    }, 1000);
  },
  getInitialState: function() {
    return getTimerState();
  },
  componentDidMount: function() {
    TimerStore.addChangeListener(this.handleChange);
    this._tick();
  },
  componentWillUnmount: function() {
    clearTimeout(this.interval);
    TimerStore.removeChangeListener(this.handleChange);
  },
  handleChange: function() {
    this.setState(getTimerState());
  },
  componentDidUpdate: function() {
    if (this.state.status === 'start' && this.interval === undefined) {
      this._tick();
    }
  },
  render: function() {
    return (
      <small className="timer">
        ({ this.state.timeLeft })
      </small>
    )
  }
});

module.exports = Timer;