uicollectionview

Take a look at these components one-by-one:

1. UICollectionView – the main view in which the content is displayed, similar to a UITableView. Note that it doesn’t necessarily have to take up the entire space inside the view controller – in the screenshot above, there’s some space above the collection view where the user can search for a term.
2. UICollectionViewCell – similartoaUITableViewCellinUITableView. Thesecells make up the content of the view and are added as subviews to the UICollectionView. Cells can either be created programmatically, inside Interface Builder, or via a combination of the two methods.
3. Supplementary Views – if you have extra information you need to display that shouldn’t be in the cells but still somewhere within the UICollectionView, you should use supplementary views. These are commonly used for headers or footers of sections.
4. Decoration View – if you want to add some extra views to enhance the visual appearance of the UICollectionView (but don’t really contain useful data), you should use decoration views. Background images or other visual embellishments are good examples of decoration views.
In addition to the above visual components, UICollectionView also has non-visual components that help with laying out content:
5. UICollectionViewLayout – UICollectionView does not know anything about how to set up cells on screen. Instead, its UICollectionViewLayout class handles this task. It uses a set of delegate methods to position every single cell in the UICollectionView. Layouts can be swapped out during runtime and the UICollectionView can even automatically animate switching from one layout to another!
6. UICollectionViewFlowLayout – You can subclass UICollectionViewLayout to create your own custom layouts (as you’ll learn about in the next tutorial), but Apple has graciously provided developers with a basic “flow-based” layout called UICollectionViewLayout. It lays elements out one after another based on their size, quite like a grid view. You can use this layout class out of the box, or subclass it to get some interesting behavior and visual effects.