以編程方式向CollectionView添加新項目，通過最後一個項目

Question

我面臨着CollectionView的一個問題，我想看到一個圖像集合，並有一個添加按鈕作爲最後一個項目，所以首先我創建了一個數組NSData的作爲我要去這些圖像保存到核心數據 var photoArray = [NSData]() 後來我實現UICollectionViewDataSource

func numberOfSections(in collectionView: UICollectionView) -> Int { 
    return 1 
} 

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) { 
    if indexPath.item == photoArray.count + 1 { 
     present(imagePicker, animated: true, completion: nil) 
    } 
} 
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 
    return photoArray.count + 1 
} 
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { 

    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "photoItem", for: indexPath) as? PhotoCell else {return UICollectionViewCell()} 
    cell.btn.tag = indexPath.item 

    if indexPath.item == photoArray.count + 1 { 
     cell.thumImage.image = UIImage(named: "add_button") 
     cell.btn.isHidden = true 
     print("first") 
     return cell 
    } else { 
     let img = photoArray[indexPath.item] 
     cell.configureAddingImage(img: img) 
     print("second") 
     return cell 

    } 
} 

其實我面臨着與「cellForItemAt indexPath」喜歡「致命錯誤的問題：指數超出範圍「我試圖讓陣列看起來像var photoArray: [NSData]!但它造成了其他問題，請給我任何建議或幫助，謝謝！

Answer 1

Index is out of range因爲項目或行從0

索引應該是這樣的：

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { 

     guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "photoItem", for: indexPath) as? PhotoCell else {return UICollectionViewCell()} 
     cell.btn.tag = indexPath.row 

     if indexPath.row == photoArray.count { 
      cell.thumImage.image = UIImage(named: "add_button") 
      cell.btn.isHidden = true 
      print("first") 
      return cell 
     } else { 
      let img = photoArray[indexPath.row] 
      cell.configureAddingImage(img: img) 
      print("second") 
      return cell 

     } 
    }