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@workInProgress
@ngdoc overview
@name Developer Guide: About MVC in Angular: Understanding the Model Component
@description
Depending on the context of the discussion in angular documentation, the term _model_ can refer to
either a single object representing one entity (for example, a model called "phones" with its value
being an array of phones) or the entire data model for the application (all entities).
In angular, a model is any data that is reachable as a property of an angular {@link
dev_guide.scopes Scope} object. The name of the property is the model identifier and the value is
any JavaScript object (including arrays and primitives).
The only requirement for a JavaScript object to be a model in angular is that the object must be
referenced by an angular scope as a property of that scope object. This property reference can be
created explicitly or implicitly.
You can create models by explicitly creating scope properties referencing JavaScript objects in the
following ways:
* Make a direct property assignment to the scope object in JavaScript code; this most commonly
occurs in controllers:
function MyCtrl() {
// create property 'foo' on the MyCtrl's scope
// and assign it an initial value 'bar'
this.foo = 'bar';
}
* Use an {@link dev_guide.expressions angular expression} with an assignment operator in templates:
<button ng:click="{{foos='ball'}}">Click me</button>
* Use {@link api/angular.directive.ng:init ng:init directive} in templates (for toy/example apps
only, not recommended for real applications):
<body ng:init=" foo = 'bar' ">
Angular creates models implicitly (by creating a scope property and assigning it a suitable value)
when processing the following template constructs:
* Form input, select, and textarea elements:
<input name="query" value="fluffy cloud">
The code above creates a model called "query" on the current scope with the value set to "fluffy
cloud".
* An iterator declaration in {@link api/angular.widget.@ng:repeat ng:repeater}:
<p ng:repeat="phone in phones"></p>
The code above creates one child scope for each item in the "phones" array and creates a "phone"
object (model) on each of these scopes with its value set to the value of "phone" in the array.
In angular, a JavaScript object stops being a model when:
* No angular scope contains a property that references the object.
* All angular scopes that contain a property referencing the object become stale and eligible for
garbage collection.
The following illustration shows a simple data model created implicitly from a simple template:
<img src="img/guide/about_model_final.png">
## Related Topics
* {@link dev_guide.mvc About MVC in Angular}
* {@link dev_guide.mvc.understanding_controller Understanding the Controller Component}
* {@link dev_guide.mvc.understanding_view Understanding the View Component}
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