在Xcode项目中使用未解析的标识符'cell'

Question

在我的匹配应用程序Xcode项目中，我指出了一个错误：

  

使用未解析的标识符“ cell”。

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

错误修复后，我应该能够在假iPhone上运行比赛应用示例。允许我点击一下翻转卡片。

Answer 1

我认为您忘记设置可重复使用的标识符

我希望这能解决您的问题。

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

Answer 2

首先，您滥用collectionView:willDisplay:forItemAt。将所有内容移至collectionView:cellForItemAt，将return替换为return cell，然后删除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
}

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

错误非常明显：您从未声明cell是didSelectItemAt的范围。更改

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