Factory does not execute $http.get - angularjs

Question

My factory does not seem to execute my $http.get. Here's my controller:
app.factory("myService", function($http) {
var myService = {
retrieve: function(id, type) {
var retrievedData = {
device: {},
childDevices: [],
error: {}
};
.
.
.
$http.get(url, headers)
.success(function(data, status) {
// some data post-processing
// some logs
})
.error(function(data, status) {
// some data post-processing
// some logs
});
return retrievedData;
};
return myService;
});
The logs within the $http.get do not print.
I read somewhere I need to use promise, but most examples I saw return $http.get directly. I don't want to return $http.get right away as I need to make some modification on the data in the factory rather than in the controller.
Thanks.

Answer 1

in angular js promise is used for returning response which come from backend. in your code retrievedData return before response come from backend. that's why angular use promise. so when response come from backend it execute success block and success block resolve the promise using deferred.resolve(data) . when error occure then error block get execute and it rejected the promise deferred.reject(err) .but when it resolve the promise it return the response data.
Service Code:
app.factory("myService", function ($http,$q) {
var myService = {
retrieve: function (id, type) {
var deferred = $q.defer();
var retrievedData = {
device: {},
childDevices: [],
error: {}
};
$http.get(url, headers).then(function (data) {
// after success this block execute
deferred.resolve(data);
},
function (err) {
//after error this block execute
deferred.reject(err);
});
return deferred.promise;
}
};
return myService;
});
controller code :
//calling retrive function
myService.retrive(id,type).then(fucntion(data){
...
})
.catch(function(){
...
})

Answer 2

Because when you return your retrievedData it hasn't been retrieved yet. That's why you should use promises:
app.factory("myService", function ($http,$q) {
var myService = {
retrieve: function (id, type) {
var deferred = $q.defer();
var retrievedData = {
device: {},
childDevices: [],
error: {}
};
$http.get(url, headers).then(function (data) {
// success do your success things here and return data
deferred.resolve(data);
},
function (err) {
deferred.reject(err);
});
return deferred.promise;
}
};
return myService;
});
// usage
myService.retrive(id,type).then(function(data){
// data retrived
})