I have a service, say:
factory('aService', ['$rootScope', '$resource', function ($rootScope, $resource) {
var service = {
foo: []
};
return service;
}]);
And I would like to use foo
to control a list that is rendered in HTML:
<div ng-controller="FooCtrl">
<div ng-repeat="item in foo">{{ item }}</div>
</div>
In order for the controller to detect when aService.foo
is updated I have cobbled together this pattern where I add aService to the controller's $scope
and then use $scope.$watch()
:
function FooCtrl($scope, aService) {
$scope.aService = aService;
$scope.foo = aService.foo;
$scope.$watch('aService.foo', function (newVal, oldVal, scope) {
if(newVal) {
scope.foo = newVal;
}
});
}
This feels long-handed, and I've been repeating it in every controller that uses the service's variables. Is there a better way to accomplish watching shared variables?
You can always use the good old observer pattern if you want to avoid the tyranny and overhead of $watch
.
In the service:
factory('aService', function() {
var observerCallbacks = [];
//register an observer
this.registerObserverCallback = function(callback){
observerCallbacks.push(callback);
};
//call this when you know 'foo' has been changed
var notifyObservers = function(){
angular.forEach(observerCallbacks, function(callback){
callback();
});
};
//example of when you may want to notify observers
this.foo = someNgResource.query().$then(function(){
notifyObservers();
});
});
And in the controller:
function FooCtrl($scope, aService){
var updateFoo = function(){
$scope.foo = aService.foo;
};
aService.registerObserverCallback(updateFoo);
//service now in control of updating foo
};