How to change space between cells in UICollectionView?

Question

I want to reduce the size between cells in row. Now it looks like:

I'm trying this, for reduce the size between them:

let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.sectionInset = UIEdgeInsets(top: 20, left: 2, bottom: 10, right: 2)
layout.minimumInteritemSpacing = 0
layout.minimumLineSpacing = 0

but it doesn't help me. What I do wrong?

Answer 1

//Objective c
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
        return CGSizeMake((collectionView.frame.size.width/3)-20, 100);
    }

// Swift 2.0

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    return CGSizeMake((collectionView.frame.size.width / 3) - 20, 100)
}

// Swift 3.0
override func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return CGSize(width: CGFloat((collectionView.frame.size.width / 3) - 20), height: CGFloat(100))
}