Reuse identifier when using two different collection views - ios

Question

Riddle me this. I have a view that I'm implementing two different collection views on. The two collection views are setup nearly identically.
When I add both to my view, my app calls an error:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'could not dequeue a view of kind: UICollectionElementKindCell with identifier CollectionViewPantsCell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard'
Which doesn't make sense, as I registered it the exact same as my CollectionViewShirtCell.
To debug, I removed the pants collection, and rewrote my "cellForItemAt" method to be really simple. It worked fine with one collectionView.
So, what is the difference? I've added some notes in caps in the code.
import UIKit
class HomeController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
let collectionViewShirtsIdentifier = "CollectionViewShirtsCell"
let collectionViewPantsIdentifier = "CollectionViewPantsCell"
var shirtStore: ShirtStore!
var pantStore: PantStore!
public var collectionViewShirts : UICollectionView{
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = UICollectionViewScrollDirection.horizontal
let collectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: view.frame.height/2), collectionViewLayout: layout)
collectionView.backgroundColor = UIColor.orange
collectionView.delegate = self
collectionView.dataSource = self
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewShirtsIdentifier)
return collectionView
}
public var collectionViewPants : UICollectionView{
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = UICollectionViewScrollDirection.horizontal
let collectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: view.frame.height/2), collectionViewLayout: layout)
collectionView.backgroundColor = UIColor.blue
collectionView.delegate = self
collectionView.dataSource = self
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewPantsIdentifier)
return collectionView
}
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.title = "Hanger"
self.view.addSubview(collectionViewShirts)
///... CANT ADD THE SECOND COLLECTION????
// self.view.addSubview(collectionViewPants)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if collectionView == self.collectionViewShirts {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: collectionViewShirtsIdentifier, for: indexPath as IndexPath)
return cell
}
else
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: collectionViewPantsIdentifier, for: indexPath as IndexPath)
return cell
}
}
///... THIS VERSION WORKS IF I ONLY TRY TO MANIPULATE ONE COLLECTION
// func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
// let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CollectionViewShirtsCell", for: indexPath as IndexPath)
//
// return cell
// }
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int{
if(collectionView == collectionViewShirts)
{
print(shirtStore.allShirts.count)
return shirtStore.allShirts.count
}
else if (collectionView == collectionViewPants)
{
return pantStore.allPants.count
}
else
{
return 5//shoeStore.allShoes.count
}
}
}

Answer 1

The way you are setting up your collectionViewShirts and collectionViewPants variables is incorrect. As a result, the if test in cellForItemAt: is falling through to the else and you are attempting to dequeue a 'pants' cell for the 'shirts' collection view.
You need to declare your collection views properly:
public var collectionViewShirts : UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = UICollectionViewScrollDirection.horizontal
let collectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: view.frame.height/2), collectionViewLayout: layout)
collectionView.backgroundColor = UIColor.orange
collectionView.delegate = self
collectionView.dataSource = self
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewShirtsIdentifier)
return collectionView
}()
public var collectionViewPants : UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = UICollectionViewScrollDirection.horizontal
let collectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: view.frame.height/2), collectionViewLayout: layout)
collectionView.backgroundColor = UIColor.blue
collectionView.delegate = self
collectionView.dataSource = self
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewPantsIdentifier)
return collectionView
}()
Note the = and the () at the end of the closure. This tells Swift to assign the value returned by invoking the anonymous function.
I would also suggest that you use constraints rather than setting the frame directly, as this won't work with view rotation and the frame won't be set correctly at the time you are initialising the collection views, as the view frame is only set when viewDidLayoutSubviews is called.
As I mentioned earlier, doing this sort of stuff in Storyboard is much simpler.