UICollectionViewCell does not take maximum width - ios

Question

I'm trying to make cells take as much width as possible, but I end up like this:
I have tried to remove margins, line spacing etc. in xcode:
But the horizontal margin is still huge, I want the same vertical margin applied.
Any ideas?
P.S attached example code:
- (void)viewDidLoad {
[super viewDidLoad];
self.collectionView.delegate = self;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return 9;
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
CollectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"Cell" forIndexPath:indexPath];
cell.backgroundColor = [UIColor whiteColor];
return cell;
}

Answer 1

You set the Collection cell to be 100x100, and to be 3 at row.
So the UICollectionView is minimum 300/300. If you make the view to be 320(normal iPhone width), then the Collection View set padding between the cells automatically.
EDIT:
Try:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
CollectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"Cell" forIndexPath:indexPath];
cell.backgroundColor = [UIColor whiteColor];
//3 because you wanted 3 cells. 18 is the min padding between the cell.
cell.frame.size.width = collectionView.frame.size.width/3-18;
return cell;
}