Why is CollectionVIew not showing inside ScrollView?

Question

iOS

Why is CollectionVIew not showing inside ScrollView? The scroll works, everything is done correctly, but the CollectionView and everything inside it is not displayed at startup. The picture shows a hierarchy. What am I doing wrong?

Answer 1

Your code? Target? Wang is not here.

Answer 2

Display the coordinates and frame of the collection view - to know where it is and what size it is.
From the received data and "dance" further: either size = 0 (constraints? content size? ..); or it is out of sight (constraints)