在 xcode 项目中使用未解析的标识符“单元格”

Question

在我的比赛应用 Xcode 项目中，我有一个错误说明：

使用未解析的标识符“单元格”。

我的代码：

import UIKit

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


    @IBOutlet weak var collectionView: UICollectionView!

    var model = CardModel()
    var cardArray:[Card] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        //call the getCards method of the card model
        cardArray = model.getCards()

        collectionView.delegate = self
        collectionView.dataSource = self

    }

    //mark: -UICollectionView Protocol Methods
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {


        return cardArray.count
    }

     func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {

        //get a cardCollectionViewcell object
        let cell =
            collectionView.dequeueReusableCell(withReuseIdentifier: "CardCell", for: indexPath) as! CardCollectionViewCell

        //get card that
        let card = cardArray[indexPath.row]

        cell.setCard(card)

        return
  }

     func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        _ = collectionView.cellForItem(at: indexPath) as!CardCollectionViewCell

        //flip the card
        cell.flip() <--------- THIS IS THE ERROR

一旦错误得到修复，我应该能够在假 iPhone 上运行匹配应用程序示例。它可以让我一键翻转卡片。

Answer 1

我想你忘了设置可重用标识符

希望这能解决您的问题。

要访问该单元格方法，您必须声明变量 let cell = collectionView.cellForItem(at: indexPath) as!CardCollectionViewCell

Answer 2

首先你误用了collectionView:willDisplay:forItemAt。将所有内容移至collectionView:cellForItemAt，将return 替换为return cell 并删除willDisplay:

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

    //get card that
    let card = cardArray[indexPath.row]
    cell.setCard(card)
    return cell
}

罢工>

   func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) { ... }

错误很明显：您从未声明 cell 是 didSelectItemAt 的范围。改变

let cell = collectionView.cellForItem(at: indexPath) as! CardCollectionViewCell