Swift v5.x Xcode 12.5
There's no storyboard, and the only XIB used is to design the collection view cell.
This is the initial view controller hierachy:
- [UINavigationController]
|-- [ViewController layout:normal]
normal: CollectionViewFlowLayout
When the button "Change Layout" is pressed, the view hierarchy changes to:
- [UINavigationController]
|-- [ViewController layout:normal]
|--[ViewController layout:expanded]
normal: CollectionViewFlowLayout
expanded: CollectionViewExpandedFlowLayout
The transition is performed via a layout-to-layout transition using Apple iOS 7 API.
The "normal" layout enforces 3 items per row on iPads, and just one item for iPhones.
The "expanded" layout enforces 1 item per row, and the item's width is the same of the collection view.
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