UICollectionViewController Error in Swift 3.0: must be initialized with a non-nil layout parameter

Question

I'm new to iOS development. I've been learning Swift, and today, I tried using UICollectionViewController.

My code is as follows:

 class ViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
    var colView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
        layout.itemSize = CGSize(width: 90, height: 120)

        colView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
        colView.dataSource = self
        colView.delegate = self
        colView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        colView.backgroundColor = UIColor.white
        self.view.addSubview(colView)
    }

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 14
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }


}

However, when I try to run it, I get the following error:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter'

I have looked up previous posts discussing this issue, but I couldn't find anything that fixed my code.

How should I fix this?

Solution 1

Thank you! I incorporated your suggestions. Below is the code that works:

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    let cellId = "CellId"
    var colView: UICollectionView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let layout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
        layout.itemSize = CGSize(width: 111, height: 111)
        
        colView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
        colView.delegate   = self
        colView.dataSource = self
        colView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        colView.backgroundColor = UIColor.white
        
        self.view.addSubview(colView)
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 21
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }
}

Again, thank you guys very much. Have an awesome day :D

Solution 2

This should work:

lazy var collectionView: UICollectionView = {
     let layout = UICollectionViewFlowLayout()
     let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
     return collectionView
}()

Solution 3

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    let cellSize = CGSize(width: 90, height: 120)
    //
    return CGSizeMake(cellSize)
}

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAtIndex section: Int) -> UIEdgeInsets {

    return UIEdgeInsetsMake(top: 20, left: 10, bottom: 10, right: 10)
}