gistfile1.txt

app.factory('api', ['$http', '$q', '$log', function($http, $q, $log) {
    return {
        last: function(market, currency){
            $log.log('api/last', currency, 'market', market);
 
            //return the promise directly.
            return $http.get('/api/last/'+market+'/'+currency)
                .then(function(result) {
                    //resolve the promise as the data
                    $log.log('api.last data', result.data);
                    return result.data;
                });
        }
        , exchanges: function(){
            //return the promise directly.
            var deferred = $q.defer();
            $http.get('/api/exchanges')
                .success(function (data) {
                    deferred.resolve(data);
                });
                
            return deferred.promise;
        }
    };
}]);

// in OrderCtrl

exchanges.then(function (data) {
  $scope.exchanges = data;
});

// or...

resolve: {
  exchanges: function ($q, api) {
    var deferred = $q.defer();
    
    api.exchange().then(function (data) {
      deferred.resolve(data.data.exchanges);
    });
    
    return deferred.promise;
  }
}