How to add an UICollectionViewLayout programmatically?

Question

I'm trying to setup a UICollectionViewLayout programmatically. I'm using a UICollectionView also without using storyboards, as well as settings its constraints.

I've followed Ray Wenderlich tutorial on the subject with some changes to adapt the code to Swift 3 (as AZCoder2 did https://github.com/AZCoder2/Pinterest).

Since all these examples uses storyboards, I've also introduced some changes to create the UICollectionView and its UICollectionViewLayout:

collectionViewLayout = PinterestLayout()
collectionViewLayout.delegate = self
collectionView = UICollectionView.init(frame: .zero, collectionViewLayout: collectionViewLayout)

The result: I can't see anything. If I change the UICollectionViewLayout with the one that Apple provides (UICollectionViewFlowLayout), at least I can see the cells with their content. If I implement some changes and use the storyboard, everything works great but it's not the way I want to accomplish this. The whole view is made programmatically and the collection view is a part of it.

What am I missing? Is it something to do with the way I instantiate the UICollectionViewLayout? Do I have to register something (for example, as I need to register the reusable cell)?

Answer 1

How about you just create a variable that creates your flow layout for you like this

var flowLayout: UICollectionViewFlowLayout {
    let _flowLayout = UICollectionViewFlowLayout()

    // edit properties here
    _flowLayout.itemSize = CGSize(width: 98, height: 134)
    _flowLayout.sectionInset = UIEdgeInsetsMake(0, 5, 0, 5)
    _flowLayout.scrollDirection = UICollectionViewScrollDirection.horizontal
    _flowLayout.minimumInteritemSpacing = 0.0
    // edit properties here

    return _flowLayout
}

And then you can set it by calling the variable.

self.collectionView.collectionViewLayout = flowLayout // after initializing it another way
// or
UICollectionView(frame: .zero, collectionViewLayout: flowLayout)

Answer 2

It's possible to do what I was trying to do. Basically, follow the tutorials I suggested in my own question and setup the collection view and its view layout as follow:

collectionViewLayout = PinterestLayout()
collectionViewLayout.delegate = self
collectionView = DynamicCollectionView.init(frame: .zero, collectionViewLayout: collectionViewLayout)

Note that I'm using DynamicCollectionView (instead of UICollectionView). This class is not provided by Apple: I've made my own using the code provided in this post.

Remember that this approach is when you're creating a view programmatically, using constraints. (May be it has another cases of use)

Answer 3

I think this will work.

override init(collectionViewLayout layout: UICollectionViewLayout) {
    super.init(collectionViewLayout: layout)
    collectionView?.collectionViewLayout = YourCollectionViewLayout()
}