UICollectionView: must be initialized with a non-nil layout parameter

Question

I added UICollectionView by code.
Now, the app crash with message: UICollectionView must be initialized with a non-nil layout parameter.
Do

Answer 1

don't setCollectionViewLayout liked this:

[self.collectionView setCollectionViewLayout:flowLayout];

try to set when init:

[[UICollectionView alloc] initWithFrame:frame collectionViewLayout:defaultLayout];