Why on Xcode 11, UICollectionViewCell changes size as soon as you scroll (I already set size in sizeForItem AtIndexPath:)?

I have collectionview inside tableview cell and I use nib for my collection view cell (in which I use autolayout for my imageview and labels and it is on Freeform mode). I'm setting cell size in tableviewcell class which is handling the delegate for collectionview inside it by this method:

 func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 200, height :150)        
    }

It always works but after Xcode 11 it doesn't.

I have the same problem. And my solution is to change the Estimate size to None in the Xcode 11.

You set collectionview Estimate size to None in Xcode 11. The reason for this is that cells in a UICollectionView can now self-size with Auto Layout constrained views in the canvas. To opt into the behavior for existing collection views, enable “Automatic” for the collection view’s estimated size, and “Automatic” for cell’s size from the Size inspector.

If deploying before iOS 13, you can activate self sizing collection view cells by calling performBatchUpdates(_:completion:) during viewDidLoad()

Ref: https://developer.apple.com/documentation/xcode_release_notes/xcode_11_release_notes

As Anh Tuan said in another answer here, you just need to change the Estimate Size to none in the Size Inspector of the Collection View from the Storyboard.

But if you wanna do this programmatically, you can try this code:

    let layout = myCollectionViewReferenceHere.collectionViewLayout as! UICollectionViewFlowLayout
    layout.estimatedItemSize = .zero