It is not possible to use the transformResponse to decorate the data with data from an asynchronous service. I posted the solution to http://jsfiddle.net/maddin/7zgz6/.
Here is the pseudo-code explaining the solution:
angular.module('myApp').service('MyService', function($q, $resource) {
var getResult = function() {
var fullResult = $q.defer();
$resource('url').get().$promise.then(function(data) {
var partialPromises = [];
for (var i = 0; i < data.elements.length; i++) {
var ires = $q.defer();
partialPromisses.push(ires);
$resource('url2').get().$promise.then(function(data2) {
//do whatever you want with data
ires.resolve(data2);
});
$q.all(partialPromisses).then(function() {
fullResult.resolve(data);
});
return fullResult.promise; // or just fullResult
}
});
};
return {
getResult: getResult
};
});