非空函数应该返回一个值

Question

I am currently trying to make a calendar and this error keeps on popping up.

I have tried return 0, and return UICollectionViewCell .

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    }

   func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {return 0}

   private func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {return }

Non-void function should return a value

Answer 1

If you want to return 0 and UICollectionViewCell, you should return them

Like this

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {

  func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
      let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "nameOfIdentifier", for: indexPath) 
      return cell
}
  func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {return 0}

Answer 2

First of all, if you're using a UICollectionView , you might need to show atleast 1 UICollectionViewCell in it.

And for that very purpose there is UICollectionViewDataSource methods.

Returning 0 in collectionView(_: numberOfItemsInSection:) won't do anything useful. Its just like I've a collectionView and don't want to show anything in it (until and unless there are specific conditions to return 0).

So, the method must return the number of cells you want to show in the collectionView .

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 1
}

Now comes the error you're facing: Non-void function should return a value .

The error is because of another UICollectionViewDataSource's methods, ie collectionView(_: cellForItemAt:) . This method expects you to return the actual collectionViewCell that'll be visible in the collectionView .

In the code you added, you're only calling return . Instead you must return an instance of UICollectionViewCell like so,

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