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A factory which creates a resource object that lets you interact with RESTful server-side data sources.

The returned resource object has action methods which provide high-level behaviors without the need to interact with the low level $http service.

Requires the `ngResource` module to be installed.

## Dependencies

- `$http`

## Usage

`$resource(url, [paramDefaults], [actions]);`

### Arguments

Param | Type | Details
--- | --- | ---
url | string | A parametrized URL template with parameters prefixed by `:` as in `/user/:username`. If you are using a URL with a port number (e.g. `http://example.com:8080/api`), it will be respected. If you are using a url with a suffix, just add the suffix, like this: `$resource('http://example.com/resource.json')` or `$resource('http://example.com/:id.json')` or even `$resource('http://example.com/resource/:resource_id.:format')` If the parameter before the suffix is empty, :resource_id in this case, then the `/.` will be collapsed down to a single `.`. If you need this sequence to appear and not collapse then you can escape it with `/\.`.
paramDefaults (optional) | Object | Default values for `url` parameters. These can be overridden in `actions` methods. If any of the parameter value is a function, it will be executed every time when a param value needs to be obtained for a request (unless the param was overridden). Each key value in the parameter object is first bound to url template if present and then any excess keys are appended to the url search query after the `?`. Given a template `/path/:verb` and parameter `{verb:'greet', salutation:'Hello'}` results in URL `/path/greet?salutation=Hello`. If the parameter value is prefixed with `@` then the value for that parameter will be extracted from the corresponding property on the `data` object (provided when calling an action method). For example, if the `defaultParam` object is `{someParam: '@someProp'}` then the value of `someParam` will be `data.someProp`.
actions (optional) | Object.<Object>= | Hash with declaration of custom action that should extend the default set of resource actions. The declaration should be created in the format of $http.config:
      {action1: {method:?, params:?, isArray:?, headers:?, ...},
       action2: {method:?, params:?, isArray:?, headers:?, ...},
       ...}
Where: `action` – {string} – The name of action. This name becomes the name of the method on your resource object. `method` – {string} – Case insensitive HTTP method (e.g. `GET`, `POST`, `PUT`, `DELETE`, `JSONP`, etc). `params` – {Object=} – Optional set of pre-bound parameters for this action. If any of the parameter value is a function, it will be executed every time when a param value needs to be obtained for a request (unless the param was overridden). `url` – {string} – action specific `url` override. The url templating is supported just like for the resource-level urls. `isArray` – {boolean=} – If true then the returned object for this action is an array, see `returns` section. `transformRequest` – `{function(data, headersGetter)|Array.<function(data, headersGetter)>}` – transform function or an array of such functions. The transform function takes the http request body and headers and returns its transformed (typically serialized) version. `transformResponse` – `{function(data, headersGetter)|Array.<function(data, headersGetter)>}` – transform function or an array of such functions. The transform function takes the http response body and headers and returns its transformed (typically deserialized) version. `cache` – `{boolean|Cache}` – If true, a default $http cache will be used to cache the GET request, otherwise if a cache instance built with $cacheFactory, this cache will be used for caching. `timeout` – `{number|Promise}` – timeout in milliseconds, or promise that should abort the request when resolved. `withCredentials` - `{boolean}` - whether to set the `withCredentials` flag on the XHR object. See requests with credentials for more information. `responseType` - `{string}` - see requestType. `interceptor` - `{Object=}` - The interceptor object has two optional methods - `response` and `responseError`. Both `response` and `responseError` interceptors get called with `http response` object. See $http interceptors.

### Returns

Object | A resource "class" object with methods for the default set of resource actions optionally extended with custom `actions`. The default set contains these actions:
      { 'get':    {method:'GET'},
        'save':   {method:'POST'},
        'query':  {method:'GET', isArray:true},
        'remove': {method:'DELETE'},
        'delete': {method:'DELETE'} };
Calling these methods invoke an `$http` with the specified http method, destination and parameters. When the data is returned from the server then the object is an instance of the resource class. The actions `save`, `remove` and `delete` are available on it as methods with the `$` prefix. This allows you to easily perform CRUD operations (create, read, update, delete) on server-side data like this:
      var User = $resource('/user/:userId', {userId:'@id'});
      var user = User.get({userId:123}, function() {
        user.abc = true;
        user.$save();
      });
It is important to realize that invoking a $resource object method immediately returns an empty reference (object or array depending on `isArray`). Once the data is returned from the server the existing reference is populated with the actual data. This is a useful trick since usually the resource is assigned to a model which is then rendered by the view. Having an empty object results in no rendering, once the data arrives from the server then the object is populated with the data and the view automatically re-renders itself showing the new data. This means that in most cases one never has to write a callback function for the action methods. The action methods on the class object or instance object can be invoked with the following parameters: HTTP GET "class" actions: `Resource.action([parameters], [success], [error])` non-GET "class" actions: `Resource.action([parameters], postData, [success], [error])` non-GET instance actions: `instance.$action([parameters], [success], [error])` Success callback is called with (value, responseHeaders) arguments. Error callback is called with (httpResponse) argument. Class actions return empty instance (with additional properties below). Instance actions return promise of the action. The Resource instances and collection have these additional properties: `$promise`: the promise of the original server interaction that created this instance or collection. On success, the promise is resolved with the same resource instance or collection object, updated with data from server. This makes it easy to use in resolve section of $routeProvider.when() to defer view rendering until the resource(s) are loaded. On failure, the promise is resolved with the http response object, without the `resource` property. If an interceptor object was provided, the promise will instead be resolved with the value returned by the interceptor. `$resolved`: `true` after first server interaction is completed (either with success or rejection), `false` before that. Knowing if the Resource has been resolved is useful in data-binding.

## Example

# Credit card resource

         // Define CreditCard class
         var CreditCard = $resource('/user/:userId/card/:cardId',
          {userId:123, cardId:'@id'}, {
           charge: {method:'POST', params:{charge:true}}
          });

         // We can retrieve a collection from the server
         var cards = CreditCard.query(function() {
           // GET: /user/123/card
           // server returns: [ {id:456, number:'1234', name:'Smith'} ];

           var card = cards[0];
           // each item is an instance of CreditCard
           expect(card instanceof CreditCard).toEqual(true);
           card.name = "J. Smith";
           // non GET methods are mapped onto the instances
           card.$save();
           // POST: /user/123/card/456 {id:456, number:'1234', name:'J. Smith'}
           // server returns: {id:456, number:'1234', name: 'J. Smith'};

           // our custom method is mapped as well.
           card.$charge({amount:9.99});
           // POST: /user/123/card/456?amount=9.99&charge=true {id:456, number:'1234', name:'J. Smith'}
         });

         // we can create an instance as well
         var newCard = new CreditCard({number:'0123'});
         newCard.name = "Mike Smith";
         newCard.$save();
         // POST: /user/123/card {number:'0123', name:'Mike Smith'}
         // server returns: {id:789, number:'0123', name: 'Mike Smith'};
         expect(newCard.id).toEqual(789);

The object returned from this function execution is a resource "class" which has "static" method for each action in the definition.

Calling these methods invoke `$http` on the `url` template with the given `method`, `params` and `headers`. When the data is returned from the server then the object is an instance of the resource type and all of the non-GET methods are available with `$` prefix. This allows you to easily support CRUD operations (create, read, update, delete) on server-side data.

         var User = $resource('/user/:userId', {userId:'@id'});
         User.get({userId:123}, function(user) {
           user.abc = true;
           user.$save();
         });

It's worth noting that the success callback for `get`, `query` and other methods gets passed in the response that came from the server as well as $http header getter function, so one could rewrite the above example and get access to http headers as:

         var User = $resource('/user/:userId', {userId:'@id'});
         User.get({userId:123}, function(u, getResponseHeaders){
           u.abc = true;
           u.$save(function(u, putResponseHeaders) {
             //u => saved user object
             //putResponseHeaders => $http header getter
           });
         });

You can also access the raw `$http` promise via the `$promise` property on the object returned

         var User = $resource('/user/:userId', {userId:'@id'});
         User.get({userId:123})
             .$promise.then(function(user) {
               $scope.user = user;
             });

# Creating a custom 'PUT' request

In this example we create a custom method on our resource to make a PUT request

       var app = angular.module('app', ['ngResource', 'ngRoute']);

       // Some APIs expect a PUT request in the format URL/object/ID
       // Here we are creating an 'update' method
       app.factory('Notes', ['$resource', function($resource) {
       return $resource('/notes/:id', null,
           {
               'update': { method:'PUT' }
           });
       }]);

       // In our controller we get the ID from the URL using ngRoute and $routeParams
       // We pass in $routeParams and our Notes factory along with $scope
       app.controller('NotesCtrl', ['$scope', '$routeParams', 'Notes',
                                          function($scope, $routeParams, Notes) {
       // First get a note object from the factory
       var note = Notes.get({ id:$routeParams.id });
       $id = note.id;

       // Now call update passing in the ID first then the object you are updating
       Notes.update({ id:$id }, note);

       // This will PUT /notes/ID with the note object in the request payload
       }]);