调用“ didSelectItemAt”时从单元格内调用函数

Question

I have a UICollection view of things. these things can have 3 states:
- Active
- Neutral
- Inactive
Now, here is the code for the UICollectionViewCell:

class NGSelectStashCell: UICollectionViewCell {
    var status: String = "Active"
    @IBOutlet weak var statusImage: UIImageView!
    @IBOutlet weak var bgImage: UIImageView!
    @IBOutlet weak var titleLabel: UILabel!

    func changeStatus()
    {
        switch status {
        case "Active":
            status = "Neutral"
            //change bgImage
        case "Neutral":
            status = "Inactive"
            //change bgImage
        case "Inactive":
            status = "Active"
            //change bgImage
        default:
            print("No Status")
        }
    }

}

Now, when I declare the UICollection View, I want to make it so that when the user "clicks" on the UICell it will call out the changeStatus() function. How can I do this in the Delegate/DataSource code?. Also, how do I save the "status" of the each cell (so that if I refresh the UICollectionView they don't all return to "active" ?

/*
 ////////// UICOLLECTIONVIEW FUNCTIONS ///////////
*/
extension NewOnlineGameVC: UICollectionViewDelegate, UICollectionViewDataSource
{
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return availableStashes.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let stashCell = collectionView.dequeueReusableCell(withReuseIdentifier: "ngStashCell", for: indexPath) as! NGSelectStashCell
        stashCell.titleLabel.text = availableStashes[indexPath.row]
        // stashCell.bgImage make image file with the same name as the name and change bg image to it.

        return stashCell
    }

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        // code to toggle between active/neutral/inactive
        // do I re-declare stashCell as! NGSelectStashCell? or what do I do?

    }
}

Answer 1

You can change the status of the cell once you get the reference of the selected cell.

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    guard let cell = collectionView.cellForItem(at: indexPath) as? NGSelectStashCell else {return}
    cell.status = "Active"
    cell.changeStatus()
}

If you want to save the status of the cell then it must be model driven ie anything happens to the cell must be saved to the model and the same model have to be reflecte in the cell when collection view tries to reuse the previously instantiated cells.

You already have a model AvailableStash, lets use it in proper way.

struct AvailableStash {
  var statusImage: UIImage?
  var backgroundImage: UIImage?
  var title: String?
  var status: String

  //Initilize properties properly
  init(with status: String) {
    self.status = status
  }
}

Your collection view must be model driven. For eg:

class DemoCollectionView: UICollectionViewController {

  var availableStashes: [AvailableStash]?

  override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return availableStashes?.count ?? 0
  }

  override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let stashCell = collectionView.dequeueReusableCell(withReuseIdentifier: "ngStashCell", for: indexPath) as! NGSelectStashCell
    let item = availableStashes[indexPath.row]
    stashCell.titleLabel.text = item
    // stashCell.bgImage make image file with the same name as the name and change bg image to it.
    stashCell.statusImage = item.statusImage
    return stashCell
  }

  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    guard let cell = collectionView.cellForItem(at: indexPath) as? NGSelectStashCell else {return}
    cell.status = availableStashes[indexPath.row].status
    cell.changeStatus()
    availableStashes[indexPath.row].status = cell.status
  }
}

Answer 2

Unfortunately the solution is a bit more complicated then you think. Collection views may queue and reuse their cells for performance gains. That means that a single cell may and will be used for multiple objects when scrolling. What will happen is that when you will change the state on first cell and will scroll so it is reused then this cell will preserve its state and will look as if another cell has this changed state...

So your source of truth must always be your data source. Whatever availableStashes contains it needs to also contain its state. So for instance if you currently have var availableStashes: [MyObject] = [] you can change it like this:

typealias MySource = (status: String, object: MyObject)
var availableStashes: [MySource] = []

func setNewObjects(objects: [MyObject]) {
    availableStashes = objects.map { ("Neutral", $0) }
}

Now on press you need to update the object in your data source for instance:

func changeStatusOfObjectAtIndex(_ index: Int, to newStatus: String) {
    availableStashes[index] = (newStatus, availableStashes[index].object)
}

So on press you do:

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    changeStatusOfObjectAtIndex(indexPath.row, to: <#Your new status here#>)
    UICollectionView().reloadItems(at: [indexPath])
}

This will now trigger a reload for this specific cell which you can now update like

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let stashCell = collectionView.dequeueReusableCell(withReuseIdentifier: "ngStashCell", for: indexPath) as! NGSelectStashCell
    stashCell.dataObject = availableStashes[indexPath.row]
    return stashCell
}

And inside the cell:

var dataObject: NewOnlineGameVC.MySource {
    didSet {
        titleLabel.text = dataObject.object
        switch dataObject.status {
        case "Active":
            //change bgImage
        case "Neutral":
            //change bgImage
        case "Inactive":
            //change bgImage
        default:
            print("No Status")
        }
    }
}

I hope this clears your issue.