Ignored constraint on iOs 7 working on ios 8

I've been struggling with this issue for hours.

I'm using a simple CollectionView which has a custom cell with custom nib file. Also I set the size of the cell by doing this:

• (CGSize)collectionView:(UICollectionView )collectionView layout:(UICollectionViewLayout)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath { return collectionView.frame.size; } I'm just trying to center a subview in the cell and so far It's working great in iOs8, the view is centered and I even call reloadData in viewWillTransitionToSize: so the cell size updates when rotating.

The Result in iOs8

But in iOs 7 it seems that the center constraint I added to the view is totally ignored.
Actually it's acting like he doesn't listen to the constraint once the cell size is changed, in the collectionView:sizeForItemAtIndexPath: method.

Giving this unpleasant result:

Am I setting the constraints correctly? did I forget something like layoutIfNeeded or needsUpdateConstraints somewhere ?

I do answer myself,

Actually I solved the problem by removing the center constraints in interface builder and adding them in code like this :

[self addConstraint:
 [NSLayoutConstraint constraintWithItem:self
                              attribute:NSLayoutAttributeCenterX
                              relatedBy:0
                                 toItem:self.connectedContainer
                              attribute:NSLayoutAttributeCenterX
                             multiplier:1
                               constant:0]];

I do not understand the -1 since this is a real issue, I'm using Xcode Version 6.0 (6A313).

I hope this will help someone having the same problem I did.