Always return data from service - angularjs

Question

I have a series of services that either fetch data from an API server, or return data if it exists in local storage.
.factory('LogEntryResource', function(config, $resource) {
return $resource(config.apiUrl + 'logentries/:id/');
})
.factory('LogEntry', function(localStorageService, LogEntryResource) {
var localLogEntries = localStorageService.get("logEntries");
return {
all: function() {
if(localLogEntries){
return localStorageService.get("logEntries");
} else {
return LogEntry.query(function(data){
localStorageService.set("logEntries", data);
return data;
});
}
},
get: function(logEntryId){
...
},
delete: function(logEntryId){
...
},
update: function(logEntryId){
...
}
}
})
The problem is that in the app controllers sometimes a promise is returned, and sometimes the data is returned, so I need to handle the return value of LogEntry.all() to either wait for the promise to resolve or to use the data.
I'm not really sure how to go about it because I can either use a .then() which works for the promise, but is undefined if it has data, or vice-versa. I know I'm doing something wrong and looking for advice how to handle this situation of dealing with either data or a promise being returned.
.controller('LogEntryCtrl', function($scope, LogEntry) {
// var data = LogEntry.all();
// var promise = LogEntry.all();
$scope.logEntry = ???
}
I'm hoping there's a nice reusable solution instead of having to do a check to see what it is every time I use this code in my controllers/routes
// trying to avoid doing this
var logEntry = LogEntry.all();
if(logEntry.isPromise){
// do promise stuff here
} else if(logEntry.isData {
// do data stuff here
}

Answer 1

My suggestion would be always return a promise. You can use $q.resolve() to create a shortcut for a resolved promise
.factory('LogEntry', function(localStorageService, LogEntry, $q) {
var localLogEntries = localStorageService.get("logEntries");
return {
all: function() {
if(localLogEntries){
return $q.resolve(localLogEntries);
} else {
return LogEntry.query(function(data){
localStorageService.set("logEntries", data);
// update variable also
localLogEntries = data;
return localLogEntries ;
});
}
},
In controller you always use then() this way
LogEntry.all().then(function(data){
$scope.data = data;
});