Locating Storyboard Views by code

Question

I've created my view by code but two UICollectionViews. So created them in the Storyboard and need to locate them by code. This is how I did it:

        TopProducts = UICollectionView(frame: CGRect(x: 8, y: scrollViewHeight + 166, width: viewWidth - 8, height: 120))
    contentScrollView.addSubview(TopProducts)

App crashes and this error shows up in the console:

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter' * First throw call stack: ( 0 CoreFoundation 0x000000010271526b exceptionPreprocess + 171 1 libobjc.A.dylib 0x000000010160af41 objc_exception_throw + 48 2 CoreFoundation 0x0000000102789ba5 +[NSException raise:format:] + 197 3 UIKit 0x0000000105d14a39 -[UICollectionView initWithFrame:collectionViewLayout:] + 81 4 UIKit 0x0000000105d149e2 -[UICollectionView initWithFrame:] + 58 5 JahanCo Catalog 0x0000000100747bfd _T0So16UICollectionViewCABSC6CGRectV5frame_tcfcTO + 77 6 JahanCo Catalog 0x0000000100744f24 _T0So16UICollectionViewCABSC6CGRectV5frame_tcfC + 100 7 JahanCo Catalog 0x00000001007446f0 _T015JahanCo_Catalog9SlideViewC11viewDidLoadyyF + 9936 8 JahanCo Catalog 0x0000000100744fa4 _T015JahanCo_Catalog9SlideViewC11viewDidLoadyyFTo + 36 9 UIKit 0x000000010542fd93 -[UIViewController loadViewIfRequired] + 1235 10 UIKit 0x0000000105476cd4 -[UINavigationController _updateScrollViewFromViewController:toViewController:] + 68 11 UIKit 0x0000000105477010 -[UINavigationController _startTransition:fromViewController:toViewController:] + 153 12 UIKit 0x0000000105478127 -[UINavigationController _startDeferredTransitionIfNeeded:] + 841 13 UIKit 0x0000000105479388 -[UINavigationController __viewWillLayoutSubviews] + 115 14 UIKit 0x00000001056c26d9 -[UILayoutContainerView layoutSubviews] + 231 15 UIKit 0x000000010536321e -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1331 16 QuartzCore 0x0000000103375c92 -[CALayer layoutSublayers] + 153 17 QuartzCore 0x0000000103379d79 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 401 18 QuartzCore 0x0000000103302851 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 385 19 QuartzCore 0x000000010332e1c2 _ZN2CA11Transaction6commitEv + 500 20 UIKit 0x00000001052b11de __34-[UIApplication _firstCommitBlock]_block_invoke_2 + 141 21 CoreFoundation 0x00000001026b82ac __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK + 12 22 CoreFoundation 0x000000010269cadb __CFRunLoopDoBlocks + 203 23 CoreFoundation 0x000000010269c2b4 __CFRunLoopRun + 1300 24 CoreFoundation 0x000000010269bb29 CFRunLoopRunSpecific + 409 25 GraphicsServices 0x000000010aa059c6 GSEventRunModal + 62 26 UIKit 0x00000001052959a4 UIApplicationMain + 159 27 JahanCo Catalog 0x0000000100754ed7 main + 55 28 libdyld.dylib 0x000000010750f621 start + 1 29 ??? 0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

Answer 1

Heres a small code snippet

import Foundation
import UIKit

class ViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDataSource {
    override func viewDidLoad() {
        super.viewDidLoad()

        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
        layout.itemSize = CGSize(width: 90, height: 120)
        let collectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        collectionView.backgroundColor = UIColor.blue
        self.view.addSubview(collectionView)
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 10
    }

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

Answer 2

Following is the way to create CollectionView Programatically

class GridViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, UICollectionViewDelegate {

override func viewDidLoad() {
    super.viewDidLoad()

    let flowLayout = UICollectionViewFlowLayout()
    //to set the scroll direction
    flowLayout.scrollDirection = .horizontal

    let collectionView = UICollectionView(frame: self.view.bounds, collectionViewLayout: flowLayout)
    collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
    collectionView.delegate = self
    collectionView.dataSource = self
    collectionView.backgroundColor = UIColor.cyan

    self.view.addSubview(collectionView)
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
    return 20
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)

    cell.backgroundColor = UIColor.green
    return cell
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
    return CGSize(width: 50, height: 50)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets
{
    return UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
}

}