AngularJS Essentials

Dependency Injection and Services
The deferred API
In order to create a new promise, we need to inject the $q service into our component
and call the $q.defer() function to instantiate a deferred object. It will be used to
implement the asynchronous behavior in a declarative way through its API. Some of
the functions are as follows:
• resolve(result): This resolves the promise with the result.
• reject(reason): This rejects the promise with a reason.
• notify(value): This provides updated information about the progress of
the promise. Consider the following code snippet:
services.js
parking.factory('carSearchService', function ($timeout, $q) {
var _filter = function (cars, criteria) {
var deferred = $q.defer();
$timeout(function () {
var result = [];
angular.forEach(cars, function (car) {
if (_matches(car, criteria)) {
result.push(car);
}
});
if (result.length > 0) {
deferred.resolve(result);
} else {
deferred.reject("No results were found!");
}
}, 1000);
return deferred.promise;
};
var _matches = function (car, criteria) {
return angular.toJson(car).indexOf(criteria) > 0;
};
return {
filter: _filter
}
});
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