how to create uicollectionview with swift programatically (without storyboard)

Question

i am trying to create a uicollectionview with swift programmatically, without any storyboard. and i need it to be multiple uicollectionview. this is my code

class jobtypeViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDataSource{
var collectionview1 = UICollectionView()
var collectionview2 = UICollectionView()

override func viewDidLoad() {
    super.viewDidLoad()

    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
    layout.itemSize = CGSize(width: 100, height: 100)

    collectionview1 = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
    self.collectionview1.delegate = self
    self.collectionview1.dataSource = self
    collectionview1.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
    self.view.addSubview(collectionview1)

    collectionview2 = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
    self.collectionview2.delegate = self
    self.collectionview2.dataSource = self
    collectionview2.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
    self.view.addSubview(collectionview2)

}

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    if collectionView == self.collectionview1 {
        return 5
    }else{
        return 4
    }
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    if collectionView == self.collectionview1 {
        let cellA = collectionview1.dequeueReusableCellWithReuseIdentifier("Cell",forIndexPath: indexPath) as UICollectionViewCell
        return cellA
    }

    else {
        let cellB = collectionview2.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as UICollectionViewCell
        return cellB
    }
}

}

everything seem fine i have the layout,delegate,and datasource, but when i run it i got this message error Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter'. did i miss something??

Answer 1

Your initializers look correct, however, your member variables are initialized with an empty initializer which will be evaluated before viewDidLoad is triggered

 var collectionview1 = UICollectionView()

You can change it to be implicitly unwrapped since you're initializing these values right away in your viewDidLoad

var collectionview1: UICollectionView!