Next/Prev Item in ng-repeat (change dynamic link?)

Hi!
i use this concept:
http://learn.ionicframework.com/formulas/sharing-data-between-views/

I would like insert two button in detail state. These buttons control the list ( < prev or next > ).

$scope.nextitem = function(){
	n = n+1;
        $scope.todo = todos[n];
};

The problem: in the detail view are data (from json) and comment button, and if i click nextitem button, data changed, but if i click comment button, this show the first clicked item comment, not the nextitem (solution maybe change dynamic url??)

or how to use next and prev item?

Thanks!