How to implement a generic HTTP service in AngularJS? - angularjs

Question

In my angular module I wrote a generic http handler for all my ajax requests.'
I was expecting that I could use the service across controllers, but my problem is the promise seems to be global.
Once ControllerOne uses the mapi_loader service, when I load AnotherController (by ng-click="go('/$route_to_load_another_controller')"), AnotherController is loaded a promise that has already returned from ControllerOne even though the URL they fetch are totally different.
So I guess my question is how do I write a service I could use across controllers? Do I really need to write a separate service for each controller where their only difference in code is the URL passed for $http.jsonp?
angular.module('myAppControllers',[])
.service('mapi_loader', ['$http', function($http) {
var promise;
var myService = {
fetch: function(url) {
if ( !promise ) {
promise = $http.jsonp(url)
.then(function (response) {
return response.data.nodes;
});
}
return promise;
}
};
return myService;
}])
.controller('ControllerOne', ['$scope', 'mapi_loader', function ($scope, mapi_loader) {
mapi_loader
.fetch("http://host.com/mapi_data_for_controller_one?callback=JSON_CALLBACK")
.then(function(data) {
$scope.useme = data;
});
}])
.controller('AnotherController', ['$scope', 'mapi_loader', function ($scope, mapi_loader) {
mapi_loader
.fetch("http://host.com/mapi_data_for_another_controller?callback=JSON_CALLBACK")
.then(function(data) {
$scope.useme = data;
});
}])
;

Answer 1

try something like this
angular.module('myAppControllers',[])
.service('mapi_loader', function($http) {
var alreadyLoading = {};
return {
fetch: function(url) {
if ( url in alreadyLoading ) {
return alreadyLoading[url];
}
return alreadyLoading[url] = $http.jsonp(url)
.then(function (response) {
delete alreadyLoading[url];
return response.data.nodes;
});
}
};
})
.controller('ControllerOne', function ($scope, mapi_loader) {
...
})
.controller('AnotherController', function ($scope, mapi_loader) {
...
});