Class Observable

addObserver (key, target, method) Ember.Observable public

Defined in packages/ember-runtime/lib/mixins/observable.js:331

key

String

The key to observe

target

Object

The target object to invoke

method

String|Function

The method to invoke

returns

Ember.Observable

Adds an observer on a property.

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

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

Observer Methods

Observer methods have the following signature:

import Component from '@ember/component';

export default Component.extend({
  init() {
    this._super(...arguments);
    this.addObserver('foo', this, 'fooDidChange');
  },

  fooDidChange(sender, key, value, rev) {
    // your code
  }
});

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.

Usually you will not need the value 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.

cacheFor (keyName) Object public

Defined in packages/ember-runtime/lib/mixins/observable.js:489

keyName

String

returns

Object

The cached value of the computed property, if any

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.

decrementProperty (keyName, decrement) Number public

Defined in packages/ember-runtime/lib/mixins/observable.js:452

keyName

String

The name of the property to decrement

decrement

Number

The amount to decrement by. Defaults to 1

returns

Number

The new property value

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

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

get (keyName) Object public

Defined in packages/ember-runtime/lib/mixins/observable.js:94

keyName

String

The property to retrieve

returns

Object

The property value or undefined.

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:

fullName: Ember.computed('firstName', 'lastName', function() {
  return this.get('firstName') + ' ' + this.get('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.

getProperties (list) Object public

Defined in packages/ember-runtime/lib/mixins/observable.js:137

list

String...|Array

of keys to get

returns

Object

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

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

is equivalent to:

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

getWithDefault (keyName, defaultValue) Object public

Defined in packages/ember-runtime/lib/mixins/observable.js:414

keyName

String

The name of the property to retrieve

defaultValue

Object

The value to return if the property value is undefined

returns

Object

The property value or the defaultValue.

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

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

incrementProperty (keyName, increment) Number public

Defined in packages/ember-runtime/lib/mixins/observable.js:432

keyName

String

The name of the property to increment

increment

Number

The amount to increment by. Defaults to 1

returns

Number

The new property value

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

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

notifyPropertyChange (keyName) Observable public

Defined in packages/ember-runtime/lib/mixins/observable.js:316

keyName

String

The property key to be notified about.

returns

Observable

Convenience method to call propertyWillChange and propertyDidChange in succession.

removeObserver (key, target, method) Ember.Observable public

Defined in packages/ember-runtime/lib/mixins/observable.js:382

key

String

The key to observe

target

Object

The target object to invoke

method

String|Function

The method to invoke

returns

Ember.Observable

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.

set (keyName, value) Object public

Defined in packages/ember-runtime/lib/mixins/observable.js:162

keyName

String

The property to set

value

Object

The value to set or `null`.

returns

Object

The passed value

Sets the provided key or path to the value.

record.set("key", 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 setUnknownProperty() 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 setUnknownProperty() handler will be called instead. This gives you an opportunity to implement complex "virtual" properties that are not predefined on the object. If setUnknownProperty() 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.

setProperties (hash) Object public

Defined in packages/ember-runtime/lib/mixins/observable.js:211

hash

Object

the hash of keys and values to set

returns

Object

The passed in hash

Sets a list of properties at once. These properties are set inside a single beginPropertyChanges and endPropertyChanges batch, so observers will be buffered.

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

toggleProperty (keyName) Boolean public

Defined in packages/ember-runtime/lib/mixins/observable.js:472

keyName

String

The name of the property to toggle

returns

Boolean

The new property value

Set the value of a boolean property to the opposite of its current value.

starship.toggleProperty('warpDriveEngaged');