Datasource on scope (not as service)

Per documentation the datasource object can be defined in two different ways.

<li ui-scroll="item in datasource">{{item}}</li>

And the directive will first look for a property with the given name (datasource) on its $scope. So to use scope-approach you need to declare datasource object on scope of your controller and define method get on it.

angular.module('application', ['ui.scroll'])
  .controller('mainController', ...

    var get = function(index, count, success) { ... };

    $scope.datasource = { get: get };

  );