Ember.Set Class
An unordered collection of objects.
A Set works a bit like an array except that its items are not ordered. You can create a set to efficiently test for membership for an object. You can also iterate through a set just like an array, even accessing objects by index, however there is no guarantee as to their order.
All Sets are observable via the Enumerable Observer API - which works on any enumerable object including both Sets and Arrays.
Creating a Set
You can create a set like you would most objects using
new Ember.Set()
. Most new sets you create will be empty, but you can
also initialize the set with some content by passing an array or other
enumerable of objects to the constructor.
Finally, you can pass in an existing set and the set will be copied. You
can also create a copy of a set by calling Ember.Set#copy()
.
// creates a new empty set
var foundNames = new Ember.Set();
// creates a set with four names in it.
var names = new Ember.Set(["Charles", "Tom", "Juan", "Alex"]); // :P
// creates a copy of the names set.
var namesCopy = new Ember.Set(names);
// same as above.
var anotherNamesCopy = names.copy();
Adding/Removing Objects
You generally add or remove objects from a set using add()
or
remove()
. You can add any type of object including primitives such as
numbers, strings, and booleans.
Unlike arrays, objects can only exist one time in a set. If you call add()
on a set with the same object multiple times, the object will only be added
once. Likewise, calling remove()
with the same object multiple times will
remove the object the first time and have no effect on future calls until
you add the object to the set again.
NOTE: You cannot add/remove null
or undefined
to a set. Any attempt to do
so will be ignored.
In addition to add/remove you can also call push()
/pop()
. Push behaves
just like add()
but pop()
, unlike remove()
will pick an arbitrary
object, remove it and return it. This is a good way to use a set as a job
queue when you don't care which order the jobs are executed in.
Testing for an Object
To test for an object's presence in a set you simply call
Ember.Set#contains()
.
Observing changes
When using Ember.Set
, you can observe the "[]"
property to be
alerted whenever the content changes. You can also add an enumerable
observer to the set to be notified of specific objects that are added and
removed from the set. See Ember.Enumerable
for more information on enumerables.
This is often unhelpful. If you are filtering sets of objects, for instance, it is very inefficient to re-filter all of the items each time the set changes. It would be better if you could just adjust the filtered set based on what was changed on the original set. The same issue applies to merging sets, as well.
Other Methods
Ember.Set
primary implements other mixin APIs. For a complete reference
on the methods you will use with Ember.Set
, please consult these mixins.
The most useful ones will be Ember.Enumerable
and
Ember.MutableEnumerable
which implement most of the common iterator
methods you are used to on Array.
Note that you can also use the Ember.Copyable
and Ember.Freezable
APIs on Ember.Set
as well. Once a set is frozen it can no longer be
modified. The benefit of this is that when you call frozenCopy()
on it,
Ember will avoid making copies of the set. This allows you to write
code that can know with certainty when the underlying set data will or
will not be modified.
Item Index
Methods
Properties
Methods
_scheduledDestroy
()
private
Invoked by the run loop to actually destroy the object. This is
scheduled for execution by the destroy
method.
add
-
obj
Adds an object to the set. Only non-null
objects can be added to a set
and those can only be added once. If the object is already in the set or
the passed value is null this method will have no effect.
This is an alias for Ember.MutableEnumerable.addObject()
.
var colors = new Ember.Set();
colors.add("blue"); // ["blue"]
colors.add("blue"); // ["blue"]
colors.add("red"); // ["blue", "red"]
colors.add(null); // ["blue", "red"]
colors.add(undefined); // ["blue", "red"]
Parameters:
-
obj
ObjectThe object to add.
Returns:
The set itself.
addEach
-
objects
Adds each object in the passed enumerable to the set.
This is an alias of Ember.MutableEnumerable.addObjects()
var colors = new Ember.Set();
colors.addEach(["red", "green", "blue"]); // ["red", "green", "blue"]
Parameters:
-
objects
Ember.Enumerablethe objects to add.
Returns:
The set itself.
addObject
-
object
Required. You must implement this method to apply this mixin.
Attempts to add the passed object to the receiver if the object is not already present in the collection. If the object is present, this method has no effect.
If the passed object is of a type not supported by the receiver, then this method should raise an exception.
Parameters:
-
object
ObjectThe object to add to the enumerable.
Returns:
the passed object
addObjects
-
objects
Adds each object in the passed enumerable to the receiver.
Parameters:
-
objects
Ember.Enumerablethe objects to add.
Returns:
receiver
clear
()
Ember.Set
Clears the set. This is useful if you want to reuse an existing set without having to recreate it.
var colors = new Ember.Set(["red", "green", "blue"]);
colors.length; // 3
colors.clear();
colors.length; // 0
Returns:
An empty Set
copy
-
deep
Override to return a copy of the receiver. Default implementation raises an exception.
Parameters:
-
deep
Booleanif
true
, a deep copy of the object should be made
Returns:
copy of receiver
destroy
()
Ember.Object
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. It will set an isDestroying flag immediately.
Returns:
receiver
eachComputedProperty
-
callback
-
binding
Iterate over each computed property for the class, passing its name
and any associated metadata (see metaForProperty
) to the callback.
Parameters:
-
callback
Function -
binding
Object
freeze
()
Object
Freezes the object. Once this method has been called the object should no longer allow any properties to be edited.
Returns:
receiver
frozenCopy
()
Object
If the object implements Ember.Freezable
, then this will return a new
copy if the object is not frozen and the receiver if the object is frozen.
Raises an exception if you try to call this method on a object that does not support freezing.
You should use this method whenever you want a copy of a freezable object since a freezable object can simply return itself without actually consuming more memory.
Returns:
copy of receiver or receiver
init
()
An overridable method called when objects are instantiated. By default, does nothing unless it is overridden during class definition.
Example:
App.Person = Ember.Object.extend({
init: function() {
alert('Name is ' + this.get('name'));
}
});
var steve = App.Person.create({
name: "Steve"
});
// alerts 'Name is Steve'.
NOTE: If you do override init
for a framework class like Ember.View
or
Ember.ArrayController
, be sure to call this._super()
in your
init
declaration! If you don't, Ember may not have an opportunity to
do important setup work, and you'll see strange behavior in your
application.
isEqual
-
obj
Returns true if the passed object is also an enumerable that contains the same objects as the receiver.
var colors = ["red", "green", "blue"],
same_colors = new Ember.Set(colors);
same_colors.isEqual(colors); // true
same_colors.isEqual(["purple", "brown"]); // false
Parameters:
-
obj
Ember.Setthe other object.
Returns:
metaForProperty
-
key
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:
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:
MyClass.metaForProperty('person');
This will return the original hash that was passed to meta()
.
Parameters:
-
key
Stringproperty name
pop
()
Object
Removes the last element from the set and returns it, or null
if it's empty.
var colors = new Ember.Set(["green", "blue"]);
colors.pop(); // "blue"
colors.pop(); // "green"
colors.pop(); // null
Returns:
The removed object from the set or null.
push
()
Ember.Set
Inserts the given object on to the end of the set. It returns the set itself.
This is an alias for Ember.MutableEnumerable.addObject()
.
var colors = new Ember.Set();
colors.push("red"); // ["red"]
colors.push("green"); // ["red", "green"]
colors.push("blue"); // ["red", "green", "blue"]
Returns:
The set itself.
remove
-
obj
Removes the object from the set if it is found. If you pass a null
value
or an object that is already not in the set, this method will have no
effect. This is an alias for Ember.MutableEnumerable.removeObject()
.
var colors = new Ember.Set(["red", "green", "blue"]);
colors.remove("red"); // ["blue", "green"]
colors.remove("purple"); // ["blue", "green"]
colors.remove(null); // ["blue", "green"]
Parameters:
-
obj
ObjectThe object to remove
Returns:
The set itself.
removeEach
-
objects
Removes each object in the passed enumerable to the set.
This is an alias of Ember.MutableEnumerable.removeObjects()
var colors = new Ember.Set(["red", "green", "blue"]);
colors.removeEach(["red", "blue"]); // ["green"]
Parameters:
-
objects
Ember.Enumerablethe objects to remove.
Returns:
The set itself.
removeObject
-
object
Required. You must implement this method to apply this mixin.
Attempts to remove the passed object from the receiver collection if the object is present in the collection. If the object is not present, this method has no effect.
If the passed object is of a type not supported by the receiver, then this method should raise an exception.
Parameters:
-
object
ObjectThe object to remove from the enumerable.
Returns:
the passed object
removeObjects
-
objects
Removes each object in the passed enumerable from the receiver.
Parameters:
-
objects
Ember.Enumerablethe objects to remove
Returns:
receiver
reopen
()
Augments a constructor's prototype with additional properties and functions:
MyObject = Ember.Object.extend({
name: 'an object'
});
o = MyObject.create();
o.get('name'); // 'an object'
MyObject.reopen({
say: function(msg){
console.log(msg);
}
})
o2 = MyObject.create();
o2.say("hello"); // logs "hello"
o.say("goodbye"); // logs "goodbye"
To add functions and properties to the constructor itself,
see reopenClass
reopenClass
()
Augments a constructor's own properties and functions:
MyObject = Ember.Object.extend({
name: 'an object'
});
MyObject.reopenClass({
canBuild: false
});
MyObject.canBuild; // false
o = MyObject.create();
In other words, this creates static properties and functions for the class. These are only available on the class and not on any instance of that class.
App.Person = Ember.Object.extend({
name : "",
sayHello : function(){
alert("Hello. My name is " + this.get('name'));
}
});
App.Person.reopenClass({
species : "Homo sapiens",
createPerson: function(newPersonsName){
return App.Person.create({
name:newPersonsName
});
}
});
var tom = App.Person.create({
name : "Tom Dale"
});
var yehuda = App.Person.createPerson("Yehuda Katz");
tom.sayHello(); // "Hello. My name is Tom Dale"
yehuda.sayHello(); // "Hello. My name is Yehuda Katz"
alert(App.Person.species); // "Homo sapiens"
Note that species
and createPerson
are not valid on the tom
and yehuda
variables. They are only valid on App.Person
.
To add functions and properties to instances of
a constructor by extending the constructor's prototype
see reopen
shift
()
Object
Removes the last element from the set and returns it, or null
if it's empty.
This is an alias for Ember.Set.pop()
.
var colors = new Ember.Set(["green", "blue"]);
colors.shift(); // "blue"
colors.shift(); // "green"
colors.shift(); // null
Returns:
The removed object from the set or null.
toString
()
String
Returns a string representation which attempts to provide more information
than Javascript's toString
typically does, in a generic way for all Ember
objects.
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:
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.
App.Teacher = App.Person.extend({
toStringExtension: function() {
return this.get('fullName');
}
});
teacher = App.Teacher.create()
teacher.toString(); //=> "<App.Teacher:ember1026:Tom Dale>"
Returns:
string representation
unshift
()
Ember.Set
Inserts the given object on to the end of the set. It returns the set itself.
This is an alias of Ember.Set.push()
var colors = new Ember.Set();
colors.unshift("red"); // ["red"]
colors.unshift("green"); // ["red", "green"]
colors.unshift("blue"); // ["red", "green", "blue"]
Returns:
The set itself.
willDestroy
()
Override to implement teardown.
Properties
concatenatedProperties
Array
Defines the properties that will be concatenated from the superclass (instead of overridden).
By default, when you extend an Ember class a property defined in
the subclass overrides a property with the same name that is defined
in the superclass. However, there are some cases where it is preferable
to build up a property's value by combining the superclass' property
value with the subclass' value. An example of this in use within Ember
is the classNames
property of Ember.View
.
Here is some sample code showing the difference between a concatenated property and a normal one:
App.BarView = Ember.View.extend({
someNonConcatenatedProperty: ['bar'],
classNames: ['bar']
});
App.FooBarView = App.BarView.extend({
someNonConcatenatedProperty: ['foo'],
classNames: ['foo'],
});
var fooBarView = App.FooBarView.create();
fooBarView.get('someNonConcatenatedProperty'); // ['foo']
fooBarView.get('classNames'); // ['ember-view', 'bar', 'foo']
This behavior extends to object creation as well. Continuing the above example:
var view = App.FooBarView.create({
someNonConcatenatedProperty: ['baz'],
classNames: ['baz']
})
view.get('someNonConcatenatedProperty'); // ['baz']
view.get('classNames'); // ['ember-view', 'bar', 'foo', 'baz']
Adding a single property that is not an array will just add it in the array:
var view = App.FooBarView.create({
classNames: 'baz'
})
view.get('classNames'); // ['ember-view', 'bar', 'foo', 'baz']
Using the concatenatedProperties
property, we can tell to Ember that mix
the content of the properties.
In Ember.View
the classNameBindings
and attributeBindings
properties
are also concatenated, in addition to classNames
.
This feature is available for you to use throughout the Ember object model, although typical app developers are likely to use it infrequently. Since it changes expectations about behavior of properties, you should properly document its usage in each individual concatenated property (to not mislead your users to think they can override the property in a subclass).
Default: null
isDestroyed
Unknown
Destroyed object property flag.
if this property is true
the observers and bindings were already
removed by the effect of calling the destroy()
method.
Default: false
isDestroying
Unknown
Destruction scheduled flag. The destroy()
method has been called.
The object stays intact until the end of the run loop at which point
the isDestroyed
flag is set.
Default: false
isFrozen
Boolean
Set to true
when the object is frozen. Use this property to detect
whether your object is frozen or not.
length
Number
This property will change as the number of objects in the set changes.
Default: 0