numberOfItemsInSection for multiple UICollectionView inside UIViewController Swift - ios

Question

I have three UICollectionView inside one UIViewController. Then I set IBOutlet for each UICollectionView
#IBOutlet weak var firstCollectionView: UICollectionView!
#IBOutlet weak var secondCollectionView: UICollectionView!
#IBOutlet weak var thirdCollectionView: UICollectionView!
and I set delegate and datasource for them. But when I want to set numberOfItemsInSection like below
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if collectionView == firstCollectionView {
return 1
} else if collectionView == secondCollectionView {
return 2
} else if collectionView == thirdCollectionView {
return 3
}
}
It keeps giving me this error Missing return in a function expected to return 'Int'

Answer 1

You need to return 0 because in numberOfItemsInSection you must have to return Int. you ended with else if but numberOfItemsInSection still need return Int value.
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if collectionView == firstCollectionView {
return 1
} else if collectionView == secondCollectionView {
return 2
} else if collectionView == thirdCollectionView {
return 3
} else {
return 0
}
}
For better readability & a little less code, I suggest you use a switch statement:
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
switch collectionView {
case firstCollectionView:
return 1
case secondCollectionView:
return 2
case thirdCollectionView:
return 3
default:
return 0
}
}

Answer 2

Personally, I'd make a separate dataSource class for each collectionView, & assign them in viewDidLoad -
firstCollectionView.dataSource = FirstDataSource()
secondCollectionView.dataSource = SecondDataSource()
thirdCollectionView.dataSource = ThirdDataSource()
& either give the required data to each dataSource when it's created or make the dataSource have responsibility for getting the data as well. Putting everything into the viewController in a situation like this leads to madness...
Simple example -
class MyDataSource: UICollectionViewDataSource {
var data: [MyData] = [] // set this when instantiating, or provide the means of creating the data which you would have put in the viewController
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.data.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
guard let cell: MyCollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellIdentifier", for: indexPath) as? MyCollectionViewCell else {
return UICollectionViewCell()
}
// do stuff to cell
}
}
In viewController -
self.firstCollectionView.dataSource = MyDataSource()
// etc...
Very straight forward, all it's doing is separating the code into areas of responsibility, makes it a whole lot easier to manage