[Q][Paginate] Is this possible to reverse sort items (limitToLast) ?

[pandaiolo]

I have a common usage of the lib for querying items to display in a infinite scrolling list. Item should be sorted by date.

I'd like to display most recent items first. What is the correct way to do this, as I cannot use limitToLast on the Scroll reference ?

Thanks !

[pandaiolo]

Maybe using Paginate instead of Scroll, and using pageCount to query the last page first, and manually sorting the results backward?

[kennycrosby]

+1 would also like to display the most recent items firs and can't seem to orderBy $id which has my timestamp

[ginovva320]

I think your only option is to use priority. I've used this with success, by setting the priority to a negative timestamp. That way, the newest items are listed first.

[katowulf]

Anything you can do here with priority, you could also do with a field on the record. Priority is not really necessary anymore as you can perform the same ops on fields.

Paginate isn't going to be able to provide descending functionality, since there is nothing in the API to provide this. A field/priority with an inverted value is the right approach.

Sorting by $id is done using orderByKey() or "$key" in the Paginate API. "$id" is an AngularFire concept, not a Firebase one.

[kennycrosby]

@katowulf thanks I didn't realize $id was AngularFire. @ginovva320 I ended up using priority to order my data, was the only way I could get it to work.

[juanpabloaj]

+1

[juanpabloaj]

@pandaiolo from this example

https://gist.github.com/katowulf/54fa9a1e713b61672f53

I use

app.controller('ctrl', function($scope, $pageArray) {
  $scope.pageItems = $pageArray(ref, 'number');

  $scope.pageItems.$loaded().then(function(){
    $scope.pageItems.page.setPage($scope.pageItems.page.pageCount);
  });
});

but I don't like this , because first load the first page and after load, change to last page.

[pandaiolo]

I have written a summary of what techniques I have come across for managing reverse order queries and pagination in Firebase. You can find it here : http://stackoverflow.com/questions/27195851/how-to-retrieve-paginated-children-in-ascending-or-descending-order-in-firebase/33484784#33484784

[mubasshir]

Hi, what is final solution for this? I'm ordering data as per timestamp. What could be better solution?

[longsangstan]

+1!!!! It seems that firebase still doesn't support reverse ordering. The firebase util infinite scroll works really nice but without reverse ordering the use of it becomes very limited.

[katowulf]

Until this feature is part of the SDK, nothing changes here. Add a field to the data with an inverted (negative) value to use descending order. Locking this thread since this isn't an fb-util issue.