NSUnknownKeyException UICollectionView

Question

最近，我为我的应用程序实现了一个新视图，它使用UICollectionView作为要加载到的图像的网格：

class MemoriesView: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource{

@IBOutlet weak var images_collection: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        self.navigationController?.navigationBarHidden = false
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 12
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("memory_image_1", forIndexPath: indexPath) as! CollectionViewController
        return cell
    }

}

现在，这个类中的代码很可能是完全颠倒的，因为我必须遵循这个教程。所以这里没有个人主动权。因此，当我试图进入这个视图时，可能会产生这个错误：

Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<Certi.MemoriesView 0x7fb613f3c8d0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key imageCollectionView.'

*** First throw call stack:
(
    0   CoreFoundation                      0x000000010ee6ae65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010f2c7deb objc_exception_throw + 48
    2   CoreFoundation                      0x000000010ee6aaa9 -[NSException raise] + 9
    3   Foundation                          0x000000010cfb29bb -[NSObject(NSKeyValueCoding) setValue:forKey:] + 288
    4   UIKit                               0x000000010d98c320 -[UIViewController setValue:forKey:] + 88
    5   UIKit                               0x000000010dbbaf41 -[UIRuntimeOutletConnection connect] + 109
    6   CoreFoundation                      0x000000010edab4a0 -[NSArray makeObjectsPerformSelector:] + 224
    7   UIKit                               0x000000010dbb9924 -[UINib instantiateWithOwner:options:] + 1864
    8   UIKit                               0x000000010d992eea -[UIViewController _loadViewFromNibNamed:bundle:] + 381
    9   UIKit                               0x000000010d993816 -[UIViewController loadView] + 178
    10  UIKit                               0x000000010d993b74 -[UIViewController loadViewIfRequired] + 138
    11  UIKit                               0x000000010d999f4f -[UIViewController __viewWillAppear:] + 120
    12  UIKit                               0x000000010d9c9e44 -[UINavigationController _startCustomTransition:] + 1203
    13  UIKit                               0x000000010d9da23f -[UINavigationController _startDeferredTransitionIfNeeded:] + 712
    14  UIKit                               0x000000010d9db3af -[UINavigationController __viewWillLayoutSubviews] + 57
    15  UIKit                               0x000000010db81ff7 -[UILayoutContainerView layoutSubviews] + 248
    16  UIKit                               0x000000010d8b44a3 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 703
    17  QuartzCore                          0x000000011101459a -[CALayer layoutSublayers] + 146
    18  QuartzCore                          0x0000000111008e70 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 366
    19  QuartzCore                          0x0000000111008cee _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
    20  QuartzCore                          0x0000000110ffd475 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 277
    21  QuartzCore                          0x000000011102ac0a _ZN2CA11Transaction6commitEv + 486
    22  UIKit                               0x000000010d7f7f7c _UIApplicationHandleEventQueue + 7329
    23  CoreFoundation                      0x000000010ed96a31 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    24  CoreFoundation                      0x000000010ed8c95c __CFRunLoopDoSources0 + 556
    25  CoreFoundation                      0x000000010ed8be13 __CFRunLoopRun + 867
    26  CoreFoundation                      0x000000010ed8b828 CFRunLoopRunSpecific + 488
    27  GraphicsServices                    0x00000001115d7ad2 GSEventRunModal + 161
    28  UIKit                               0x000000010d7fd610 UIApplicationMain + 171
    29  Certi                               0x000000010b92c1fd main + 109
    30  libdyld.dylib                       0x000000010fde392d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

我怀疑您确实将我们的IBOutlet imageCollectionView重命名为images_collection，但没有在Storyboard中更新。

要解决这个问题：

• 右键单击童话板中的imageCollectionView
• 单击"x“按钮移除指向Memories View的链接

​

​

• 通过从代码中的IBOutlet拖动到故事板中的imageCollectionView创建一个新链接

​

​

Answer 2

这一职能的问题是：

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("memory_image_1", forIndexPath: indexPath) as! CollectionViewController

return cell

您正在尝试将UICollectionViewCell转换为CollectionViewController。对该行末尾的简单更改：

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("memory_image_1", forIndexPath: indexPath) as! UICollectionViewCell
// see below
return cell

将防止此错误，但仍将获得空白单元格。在我添加注释\\ see below的地方，您需要更新cell的值，以选择在该行上显示的内容。如果使用多个节，则可以从indexPath.row和indexPath.section确定行。

另外，如果要为单元格使用自定义类，它处理的是默认视图以外的视图，则需要将cell转换为自定义类，而不是UICollectionViewController，尽管我假设您仍然在查看教程--这还不是您将要尝试的。

正如我在对这个问题的评论中所指出的，这个网站上的教程-- https://www.raywenderlich.com/136159/uicollectionview-tutorial-getting-started和其他教程--对于初学者来说是非常好的。