更新CollectionView未选中的单元格？

Question

我有一个CollectionView，允许用户触摸一个单元格，它会更改边框颜色。但是，我一次只想选择一个单元格。如何编辑此代码，以便使用边框颜色更新indexpath处的单元格，并且之前选定的单元格将被重置？

override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) { 

     self.user["avatar"] = self.avatars[indexPath.row] 

     do { 
      try self.user.save() 
     } catch { 
      print(error) 
     } 

     let cell = collectionView.cellForItemAtIndexPath(indexPath) as! AvatarViewCell 
     cell.layer.borderWidth = 5.0 
     cell.layer.borderColor = UIColor.purpleColor().CGColor 

谢谢！

UPDATE

 let cell = collectionView.cellForItemAtIndexPath(indexPath) as! AvatarViewCell 
     var previouslySelectedIndexPath: NSIndexPath? 
     if previouslySelectedIndexPath != nil { 
      let previousCell = collectionView.cellForItemAtIndexPath(previouslySelectedIndexPath!) as! AvatarViewCell 
      previousCell.layer.borderWidth = 0 
      previousCell.layer.borderColor = UIColor.whiteColor().CGColor 
     } 

     cell.layer.borderWidth = 5.0 
     cell.layer.borderColor = UIColor.purpleColor().CGColor 

Answer 1

你为什么不有一个实例变量（在类文件的开头添加）每次都存先前选定的单元格

var previouslySelectedIndexPath: NSIndexPath? 

然后一个新的小区被选中时，首先删除先前选定单元格的边框，然后将边框添加到新选单元格

if previouslySelectedIndexPath != nil { 
    let previousCell = collectionView.cellForItemAtIndexPath(previouslySelectedIndexPath!) as! AvatarViewCell 
    previousCell.borderWidth = 0 
} 
let currentCell = collectionView.cellForItemAtIndexPath(indexPath) as! AvatarViewCell 
cell.layer.borderWidth = 5.0 
cell.layer.borderColor = UIColor.purpleColor().CGColor 
previouslySelectedIndexPath = indexPath 

Answer 2

您可以实现

func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) 

下面是一个使用香草UICollectionViewCell一个例子：

// MARK: UICollectionViewDelegate 

override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) { 

    if let cell = collectionView.cellForItemAtIndexPath(indexPath) { 
     cell.layer.borderWidth = 5.0 
     cell.layer.borderColor = UIColor.purpleColor().CGColor 
    } 
} 

override func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) { 

    if let cell = collectionView.cellForItemAtIndexPath(indexPath) { 
     cell.layer.borderWidth = 0 
     cell.layer.borderColor = UIColor.whiteColor().CGColor 
    } 
}