scheduler.md

Rx.Scheduler class

Provides a set of static methods to access commonly used schedulers and a base class for all schedulers.

Usage

The follow example shows the basic usage of an Rx.Scheduler.

var disposable = Rx.Scheduler.timeout.scheduleWithState(
     'world', 
     function (x) {
          console.log('hello ' + x);
     }
);

// => hello world

Location

• rx.js

Scheduler Constructor

• constructor

Scheduler Instance Methods

• catchException
• now

Standard Scheduling

• schedule
• scheduleWithState
• scheduleWithAbsolute
• scheduleWithAbsoluteAndState
• scheduleWithRelative
• scheduleWithRelativeAndState

Recursive Scheduling

• scheduleRecursive
• scheduleRecursiveWithState
• scheduleRecursiveWithAbsolute
• scheduleRecursiveWithAbsoluteAndState
• scheduleRecursiveWithRelative
• scheduleRecursiveWithRelativeAndState

Periodic Scheduling

• schedulePeriodic
• schedulePeriodicWithState

`Scheduler Class Methods

• normalize

Scheduler Class Properties

• currentThread
• immediate
• timeout

Scheduler Constructor

Rx.Scheduler(now, schedule, scheduleRelative, scheduleAbsolute)

# Ⓢ

Initializes a new instance of the Rx.Scheduler. This is meant for Scheduler implementers and not normal usage.

Arguments

1. now (Function): Function which gets the current time according to the local machine's system clock.
2. schedule (Function): Function to schedule an action immediately.
3. scheduleRelative (Function): Function used to schedule an action in relative time.
4. scheduleAbsolute (Function): Function used to schedule an action in absolute time.

Example

// Used for scheduling immediately
function schedule(state, action) {
     var scheduler = this,
          disposable = new Rx.SingleAssignmentDisposable();

     var id = setTimeout(function () {
          if (!disposable.isDisposed) {
               disposable.setDisposable(action(scheduler, state));
          }
     }, 0);

     return new CompositeDisposable(disposable, disposableCreate(function () {
          clearMethod(id);
     }));
}

// Used for scheduling relative to now
function scheduleRelative(state, dueTime, action) {
     var scheduler = this,
          dt = Scheduler.normalize(dueTime);

     // Shortcut if already 0
     if (dt === 0) {
          return scheduler.scheduleWithState(state, action);
     }

     var disposable = new Rx.SingleAssignmentDisposable();
     var id = window.setTimeout(function () {
          if (!disposable.isDisposed) {
               disposable.setDisposable(action(scheduler, state));
          }
     }, dt);
  
     return new CompositeDisposable(disposable, disposableCreate(function () {
          window.clearTimeout(id);
     }));
}

// Used for scheduling in absolute time
function scheduleAbsolute(state, dueTime, action) {
     return this.scheduleWithRelativeAndState(state, dueTime - this.now(), action);
}

var timeoutScheduler = new Rx.Scheduler(
     Date.now,
     schedule,
     scheduleRelative,
     scheduleAbsolute
);

var handle = timeoutScheduler.schedule(function () {
     console.log('hello');
});

// => hello

Location

• rx.js

---

Scheduler Instance Methods

Rx.Scheduler.prototype.catch(handler)

# Ⓢ

Returns a scheduler that wraps the original scheduler, adding exception handling for scheduled actions. There is an alias of catchException for browsers < IE9.

Arguments

1. handler (Function): Handler that's run if an exception is caught. The exception will be rethrown if the handler returns false.

Returns

(Scheduler): Wrapper around the original scheduler, enforcing exception handling.

Example

function inherits (ctor, superCtor) {
    ctor.super_ = superCtor;
    ctor.prototype = Object.create(superCtor.prototype, {
        constructor: {
            value: ctor,
            enumerable: false,
            writable: true,
            configurable: true
        }
    });
}

inherits (SchedulerError, Error);

function SchedulerError(message) {
    Error.call(this, message);   
}

var scheduler = Rx.Scheduler.timeout;
var catchScheduler = scheduler.catchException(function (e) {
    return e instanceof SchedulerError;
});

// Throws no exception
var d1 = catchScheduler.schedule(function () {
    throw new SchedulerError('woops'); 
});

var d2 = catchScheduler.schedule(function () {
    throw new Error('woops'); 
});

// => Uncaught Error: woops

Location

• rx.js

---

Rx.Scheduler.prototype.now()

# Ⓢ

Gets the current time according to the Scheduler implementation.

Returns

(Number): The current time according to the Scheduler implementation.

Example

var now = Rx.Scheduler.timeout.now();

console.log(now);
// => 1381806323143

Location

• rx.js

---

Standard Scheduling

Rx.Scheduler.prototype.schedule(action)

# Ⓢ

Schedules an action to be executed.

Arguments

1. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.immediate.schedule(function () {
     console.log('hello');  
});

// => hello

// Tries to cancel but too late since it is immediate
disposable.dispose();

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleWithState(state, action)

# Ⓢ

Schedules an action to be executed with state.

Arguments

1. state (Any): State passed to the action to be executed.
2. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.immediate.scheduleWithState('world', function (x) {
     console.log('hello ' + x);  
});

// => hello world

// Tries to cancel but too late since it is immediate
disposable.dispose();

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleWithAbsolute(duetime, action)

# Ⓢ

Schedules an action to be executed at the specified absolute due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. dueTime (Number): Absolute time at which to execute the action.
2. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.scheduleWithAbsolute(
     Date.now() + 5000, /* 5 seconds in the future */
     function () {
          console.log('hello');  
     }
);

// => hello

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleWithAbsoluteAndState(state, duetime, action)

# Ⓢ

Schedules an action to be executed at the specified absolute due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. state (Any): State passed to the action to be executed.
2. dueTime (Number): Absolute time at which to execute the action.
3. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.scheduleWithAbsolute(
     'world',
     Date.now() + 5000, /* 5 seconds in the future */
     function (x) {
          console.log('hello ' + x);  
     }
);

// => hello world

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleWithRelative(duetime, action)

# Ⓢ

Schedules an action to be executed after the specified relative due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. dueTime (Number): Relative time at which to execute the action.
2. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.scheduleWithRelative(
     5000, /* 5 seconds in the future */
     function () {
          console.log('hello');  
     }
);

// => hello

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleWithRelativeAndState(state, duetime, action)

# Ⓢ

Schedules an action to be executed at the specified relative due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. state (Any): State passed to the action to be executed.
2. dueTime (Number): Relative time at which to execute the action.
3. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.scheduleWithAbsolute(
     'world',
     5000, /* 5 seconds in the future */
     function (x) {
          console.log('hello ' + x);  
     }
);

// => hello world

Location

• rx.js

---

Recursive Scheduling

Rx.Scheduler.prototype.scheduleRecursive(action)

# Ⓢ

Schedules an action to be executed recursively.

Arguments

1. action (Function): Action to execute recursively. The parameter passed to the action is used to trigger recursive scheduling of the action.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var i = 0;

var disposable = Rx.Scheduler.immediate.scheduleRecursive(
     function (self) {
          console.log(i);
          if (++i < 3) {
               self(i);
          } 
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleRecursiveWithState(state, action)

# Ⓢ

Schedules an action to be executed with state.

Arguments

1. state (Any): State passed to the action to be executed.
2. action (Function): Action to execute recursively. The last parameter passed to the action is used to trigger recursive scheduling of the action, passing in recursive invocation state.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.immediate.scheduleRecursiveWithState(
     0, 
     function (i, self) {
          console.log(i);
          if (++i < 3) {
               self(i);
          } 
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleRecursiveWithAbsolute(duetime, action)

# Ⓢ

Schedules an action to be executed recursively at a specified absolute due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. dueTime (Number): Absolute time at which to execute the action for the first time.
2. action (Function): Action to execute recursively. The parameter passed to the action is used to trigger recursive scheduling of the action at the specified absolute time.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var i = 0;

var disposable = Rx.Scheduler.timeout.scheduleRecursiveWithAbsolute(
     Date.now() + 5000, /* 5 seconds in the future */
     function (self) {
          console.log(i);
          if (++i < 3) {
               // Schedule mutliplied by a second by position
               self(Date.now() + (i * 1000));
          } 
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleRecursiveWithAbsoluteAndState(state, duetime, action)

# Ⓢ

Schedules an action to be executed recursively at a specified absolute due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. state (Any): State passed to the action to be executed.
2. dueTime (Number): Absolute time at which to execute the action for the first time.
3. action (Function): Action to execute recursively. The last parameter passed to the action is used to trigger recursive scheduling of the action, passing in the recursive due time and invocation state.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.scheduleRecursiveWithAbsoluteAndState(
     0,
     Date.now() + 5000, /* 5 seconds in the future */
     function (i, self) {
          console.log(i);
          if (++i < 3) {
               // Schedule mutliplied by a second by position
               self(i, Date.now() + (i * 1000));
          } 
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleRecursiveWithRelative(duetime, action)

# Ⓢ

Schedules an action to be executed recursively at a specified relative due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. dueTime (Number): Relative time at which to execute the action for the first time.
2. action (Function): Action to execute recursively. The parameter passed to the action is used to trigger recursive scheduling of the action at the specified relative time.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var i = 0;

var disposable = Rx.Scheduler.timeout.scheduleRecursiveWithRelative(
     5000, /* 5 seconds in the future */
     function (self) {
          console.log(i);
          if (++i < 3) {
               // Schedule mutliplied by a second by position
               self(i * 1000);
          } 
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Rx.Scheduler.prototype.scheduleRecursiveWithAbsoluteAndState(state, duetime, action)

# Ⓢ

Schedules an action to be executed recursively at a specified relative due time. Note this only works with the built-in Rx.Scheduler.timeout scheduler, as the rest will throw an exception as the framework does not allow for blocking.

Arguments

1. state (Any): State passed to the action to be executed.
2. dueTime (Number): Relative time at which to execute the action for the first time.
3. action (Function): Action to execute recursively. The last parameter passed to the action is used to trigger recursive scheduling of the action, passing in the recursive due time and invocation state.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.scheduleRecursiveWithRelativeAndState(
     0,
     5000, /* 5 seconds in the future */
     function (i, self) {
          console.log(i);
          if (++i < 3) {
               // Schedule mutliplied by a second by position
               self(i, i * 1000);
          } 
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Periodic Scheduling

Rx.Scheduler.prototype.schedulePeriodic(period, action)

# Ⓢ

Schedules a periodic piece of work by dynamically discovering the scheduler's capabilities. The periodic task will be scheduled using window.setInterval for the base implementation.

Arguments

1. period (Number): Period for running the work periodically in ms.
2. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var i = 0;

var disposable = Rx.Scheduler.timeout.schedulePeriodic(
     1000, /* 1 second */ 
     function () {
          console.log(i);

          // After three times, dispose
          if (++i > 3) {
               disposable.dispose();
          }
});

// => 0
// => 1
// => 2
// => 3

Location

• rx.js

---

Rx.Scheduler.prototype.schedulePeriodicWithState(state, period, action)

# Ⓢ

Schedules a periodic piece of work by dynamically discovering the scheduler's capabilities. The periodic task will be scheduled using window.setInterval for the base implementation.

Arguments

1. state (Any): State passed to the action to be executed.
2. period (Number): Period for running the work periodically in ms.
3. action (Function): Action to execute.

Returns

(Disposable): The disposable object used to cancel the scheduled action (best effort).

Example

var disposable = Rx.Scheduler.timeout.schedulePeriodicWithState(
     0,
     1000, /* 1 second */ 
     function (i) {
          console.log(i);

          // After three times, dispose
          if (++i > 3) {
               disposable.dispose();
          }

          return i;
});

// => 0
// => 1
// => 2
// => 3

Location

• rx.js

---

Scheduler Class Methods

Rx.Scheduler.normalize(dueTime)

# Ⓢ

Normalizes the specified time span value to a positive value.

Arguments

1. dueTime (Number): The time span value to normalize.

Returns

(Number): The specified time span value if it is zero or positive; otherwise, 0

Example

var r1 = Rx.Scheduler.normalize(-1);
console.log(r1);
// => 0

var r2 = Rx.Scheduler.normalize(255);
console.log(r1);
// => 255

Location

• rx.js

---

Scheduler Class Properties

Rx.Scheduler.currentThread

# Ⓢ

Gets a scheduler that schedules work as soon as possible on the current thread. This implementation does not support relative and absolute scheduling due to thread blocking required.

Example

var scheduler = Rx.Scheduler.currentThread;

var disposable = scheduler.scheduleWithState(
     'world',
     function (x) {
          console.log('hello ' + x);
     });

// => hello world

Location

• rx.js

---

Rx.Scheduler.immediate

# Ⓢ

Gets a scheduler that schedules work immediately on the current thread.

Example

var scheduler = Rx.Scheduler.immediate;

var disposable = scheduler.scheduleRecursiveWithState(
     0,
     function (x, self) {
          console.log(x);
          if (++x < 3) {
               self(x);
          }
     }
);

// => 0
// => 1
// => 2

Location

• rx.js

---

Rx.Scheduler.timeout

# Ⓢ

Gets a scheduler that schedules work via a timed callback based upon platform.

For all schedule calls, it defaults to:

• Node.js: uses setImmediate for newer builds, and process.nextTick for older versions.
• Browser: depending on platform may use setImmediate, MessageChannel, window.postMessage and for older versions of IE, it will default to script.onreadystatechanged, else falls back to window.setTimeout.

For all relative and absolute scheduling, it defaults to using window.setTimeout.

Example

var scheduler = Rx.Scheduler.timeout;

var disposable = scheduler.scheduleWithState(
     0,
     function (x) {
          console.log(x);
     }
);

// => 0

Location

• rx.js

---