Ember.StateManager Class

Adds an observer on a property.

This is the core method used to register an observer for a property.

Once you call this method, anytime the key's value is set, your observer will be notified. Note that the observers are triggered anytime the value is set, regardless of whether it has actually changed. Your observer should be prepared to handle that.

You can also pass an optional context parameter to this method. The context will be passed to your observer method whenever it is triggered. Note that if you add the same target/method pair on a key multiple times with different context parameters, your observer will only be called once with the last context you passed.

Observer Methods

Observer methods you pass should generally have the following signature if you do not pass a context parameter:

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fooDidChange: function(sender, key, value, rev) { };

The sender is the object that changed. The key is the property that changes. The value property is currently reserved and unused. The rev is the last property revision of the object when it changed, which you can use to detect if the key value has really changed or not.

If you pass a context parameter, the context will be passed before the revision like so:

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fooDidChange: function(sender, key, value, context, rev) { };

Usually you will not need the value, context or revision parameters at the end. In this case, it is common to write observer methods that take only a sender and key value as parameters or, if you aren't interested in any of these values, to write an observer that has no parameters at all.

Begins a grouping of property changes.

You can use this method to group property changes so that notifications will not be sent until the changes are finished. If you plan to make a large number of changes to an object at one time, you should call this method at the beginning of the changes to begin deferring change notifications. When you are done making changes, call endPropertyChanges() to deliver the deferred change notifications and end deferring.

Returns the cached value of a computed property, if it exists. This allows you to inspect the value of a computed property without accidentally invoking it if it is intended to be generated lazily.

Creates an instance of a class. Accepts either no arguments, or an object containing values to initialize the newly instantiated object with.

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App.Person = Ember.Object.extend({
  helloWorld: function() {
    alert("Hi, my name is " + this.get('name'));
  }
});

var tom = App.Person.create({
  name: 'Tom Dale'
});

tom.helloWorld(); // alerts "Hi, my name is Tom Dale".

create will call the init function if defined during Ember.AnyObject.extend

If no arguments are passed to create, it will not set values to the new instance during initialization:

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var noName = App.Person.create();
noName.helloWorld(); // alerts undefined

NOTE: For performance reasons, you cannot declare methods or computed properties during create. You should instead declare methods and computed properties when using extend.

Set the value of a property to the current value minus some amount.

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player.decrementProperty('lives');
orc.decrementProperty('health', 5);

Destroys an object by setting the isDestroyed flag and removing its metadata, which effectively destroys observers and bindings.

If you try to set a property on a destroyed object, an exception will be raised.

Note that destruction is scheduled for the end of the run loop and does not happen immediately.

Iterate over each computed property for the class, passing its name and any associated metadata (see metaForProperty) to the callback.

Ends a grouping of property changes.

You can use this method to group property changes so that notifications will not be sent until the changes are finished. If you plan to make a large number of changes to an object at one time, you should call beginPropertyChanges() at the beginning of the changes to defer change notifications. When you are done making changes, call this method to deliver the deferred change notifications and end deferring.

Retrieves the value of a property from the object.

This method is usually similar to using object[keyName] or object.keyName, however it supports both computed properties and the unknownProperty handler.

Because get unifies the syntax for accessing all these kinds of properties, it can make many refactorings easier, such as replacing a simple property with a computed property, or vice versa.

Computed Properties

Computed properties are methods defined with the property modifier declared at the end, such as:

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fullName: function() {
  return this.getEach('firstName', 'lastName').compact().join(' ');
}.property('firstName', 'lastName')

When you call get on a computed property, the function will be called and the return value will be returned instead of the function itself.

Unknown Properties

Likewise, if you try to call get on a property whose value is undefined, the unknownProperty() method will be called on the object. If this method returns any value other than undefined, it will be returned instead. This allows you to implement "virtual" properties that are not defined upfront.

To get multiple properties at once, call getProperties with a list of strings or an array:

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record.getProperties('firstName', 'lastName', 'zipCode');  // { firstName: 'John', lastName: 'Doe', zipCode: '10011' }

is equivalent to:

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record.getProperties(['firstName', 'lastName', 'zipCode']);  // { firstName: 'John', lastName: 'Doe', zipCode: '10011' }

Retrieves the value of a property, or a default value in the case that the property returns undefined.

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person.getWithDefault('lastName', 'Doe');

Checks to see if object has any subscriptions for named event.

Returns true if the object currently has observers registered for a particular key. You can use this method to potentially defer performing an expensive action until someone begins observing a particular property on the object.

Set the value of a property to the current value plus some amount.

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person.incrementProperty('age');
team.incrementProperty('score', 2);

In some cases, you may want to annotate computed properties with additional metadata about how they function or what values they operate on. For example, computed property functions may close over variables that are then no longer available for introspection.

You can pass a hash of these values to a computed property like this:

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person: function() {
  var personId = this.get('personId');
  return App.Person.create({ id: personId });
}.property().meta({ type: App.Person })

Once you've done this, you can retrieve the values saved to the computed property from your class like this:

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MyClass.metaForProperty('person');

This will return the original hash that was passed to meta().

Convenience method to call propertyWillChange and propertyDidChange in succession.

Cancels subscription for give name, target, and method.

Subscribes to a named event with given function.

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person.on('didLoad', function() {
  // fired once the person has loaded
});

An optional target can be passed in as the 2nd argument that will be set as the "this" for the callback. This is a good way to give your function access to the object triggering the event. When the target parameter is used the callback becomes the third argument.

Subscribes a function to a named event and then cancels the subscription after the first time the event is triggered. It is good to use one when you only care about the first time an event has taken place.

This function takes an optional 2nd argument that will become the "this" value for the callback. If this argument is passed then the 3rd argument becomes the function.

Notify the observer system that a property has just changed.

Sometimes you need to change a value directly or indirectly without actually calling get() or set() on it. In this case, you can use this method and propertyWillChange() instead. Calling these two methods together will notify all observers that the property has potentially changed value.

Note that you must always call propertyWillChange and propertyDidChange as a pair. If you do not, it may get the property change groups out of order and cause notifications to be delivered more often than you would like.

Notify the observer system that a property is about to change.

Sometimes you need to change a value directly or indirectly without actually calling get() or set() on it. In this case, you can use this method and propertyDidChange() instead. Calling these two methods together will notify all observers that the property has potentially changed value.

Note that you must always call propertyWillChange and propertyDidChange as a pair. If you do not, it may get the property change groups out of order and cause notifications to be delivered more often than you would like.

Remove an observer you have previously registered on this object. Pass the same key, target, and method you passed to addObserver() and your target will no longer receive notifications.

Sets the provided key or path to the value.

This method is generally very similar to calling object[key] = value or object.key = value, except that it provides support for computed properties, the unknownProperty() method and property observers.

Computed Properties

If you try to set a value on a key that has a computed property handler defined (see the get() method for an example), then set() will call that method, passing both the value and key instead of simply changing the value itself. This is useful for those times when you need to implement a property that is composed of one or more member properties.

Unknown Properties

If you try to set a value on a key that is undefined in the target object, then the unknownProperty() handler will be called instead. This gives you an opportunity to implement complex "virtual" properties that are not predefined on the object. If unknownProperty() returns undefined, then set() will simply set the value on the object.

Property Observers

In addition to changing the property, set() will also register a property change with the object. Unless you have placed this call inside of a beginPropertyChanges() and endPropertyChanges(), any "local" observers (i.e. observer methods declared on the same object), will be called immediately. Any "remote" observers (i.e. observer methods declared on another object) will be placed in a queue and called at a later time in a coalesced manner.

Chaining

In addition to property changes, set() returns the value of the object itself so you can do chaining like this:

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record.set('firstName', 'Charles').set('lastName', 'Jolley');

To set multiple properties at once, call setProperties with a Hash:

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record.setProperties({ firstName: 'Charles', lastName: 'Jolley' });

Returns a string representation which attempts to provide more information than Javascript's toString typically does, in a generic way for all Ember objects.

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App.Person = Em.Object.extend()
person = App.Person.create()
person.toString() //=> "<App.Person:ember1024>"

If the object's class is not defined on an Ember namespace, it will indicate it is a subclass of the registered superclass:

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Student = App.Person.extend()
student = Student.create()
student.toString() //=> "<(subclass of App.Person):ember1025>"

If the method toStringExtension is defined, its return value will be included in the output.

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App.Teacher = App.Person.extend({
  toStringExtension: function(){
    return this.get('fullName');
  }
});
teacher = App.Teacher.create()
teacher.toString(); //=> "<App.Teacher:ember1026:Tom Dale>"

Set the value of a boolean property to the opposite of it's current value.

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starship.toggleProperty('warpDriveEnaged');

Creates an action function for transitioning to the named state while preserving context.

The following example StateManagers are equivalent:

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aManager = Ember.StateManager.create({
  stateOne: Ember.State.create({
    changeToStateTwo: Ember.State.transitionTo('stateTwo')
  }),
  stateTwo: Ember.State.create({})
})

bManager = Ember.StateManager.create({
  stateOne: Ember.State.create({
    changeToStateTwo: function(manager, context){
      manager.transitionTo('stateTwo', context)
    }
  }),
  stateTwo: Ember.State.create({})
})