Swift UITableView 无法识别的选择器发送到实例

Posted 2023-03-12

【中文标题】Swift UITableView 无法识别的选择器发送到实例

【英文标题】：Swift UITableView unrecognized selector sent to instance

【发布时间】：2015-07-15 15:31:20

【问题描述】：

在我的选项卡式应用程序中，第一个选项卡是一个导航控制器，它显示聊天会话的表格视图 (ChatsViewController)。在视图控制器中，因为我使用 Parse 作为后端，所以我测试 PFUser.currentUser() 是否为 nil，如果是，则我提供一个身份验证视图控制器。但是，打开应用程序后，它会在启动屏幕后立即崩溃。这是控制台输出：

1
2
2015-07-15 11:13:55.251 Chat App[1116:90011] Presenting view controllers on detached view controllers is discouraged <Chat_App.ChatsViewController: 0x7fade2442fa0>.
3
2015-07-15 11:13:55.256 Chat App[1116:90011] -[UIView tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x7fade262ec70
2015-07-15 11:13:55.264 Chat App[1116:90011] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIView tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x7fade262ec70'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000106a3bc65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x00000001085a6bb7 objc_exception_throw + 45
    2   CoreFoundation                      0x0000000106a430ad -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x000000010699913c ___forwarding___ + 988
    4   CoreFoundation                      0x0000000106998cd8 _CF_forwarding_prep_0 + 120
    5   UIKit                               0x0000000107564252 -[UISectionRowData refreshWithSection:tableView:tableViewRowData:] + 2353
    6   UIKit                               0x0000000107569edc -[UITableViewRowData rectForFooterInSection:heightCanBeGuessed:] + 324
    7   UIKit                               0x000000010756a020 -[UITableViewRowData heightForTable] + 56
    8   UIKit                               0x00000001073b3720 -[UITableView _updateContentSize] + 381
    9   UIKit                               0x00000001073d34b2 -[UITableView _rebuildGeometry] + 40
    10  UIKit                               0x00000001073d18b0 -[UITableView didMoveToWindow] + 104
    11  UIKit                               0x0000000107355a28 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 1496
    12  UIKit                               0x000000010736748b -[UIScrollView _didMoveFromWindow:toWindow:] + 55
    13  UIKit                               0x000000010735570a -[UIView(Internal) _didMoveFromWindow:toWindow:] + 698
    14  UIKit                               0x000000010735570a -[UIView(Internal) _didMoveFromWindow:toWindow:] + 698
    15  UIKit                               0x000000010734de8f __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 125
    16  UIKit                               0x000000010734de03 -[UIView(Hierarchy) _postMovedFromSuperview:] + 437
    17  UIKit                               0x0000000107357f08 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1660
    18  UIKit                               0x000000010763e80c -[UINavigationTransitionView transition:fromView:toView:] + 479
    19  UIKit                               0x000000010743c170 -[UINavigationController _startTransition:fromViewController:toViewController:] + 2984
    20  UIKit                               0x000000010743c408 -[UINavigationController _startDeferredTransitionIfNeeded:] + 523
    21  UIKit                               0x000000010743cece -[UINavigationController __viewWillLayoutSubviews] + 43
    22  UIKit                               0x00000001075876d5 -[UILayoutContainerView layoutSubviews] + 202
    23  UIKit                               0x000000010735a9eb -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 536
    24  QuartzCore                          0x000000010663bed2 -[CALayer layoutSublayers] + 146
    25  QuartzCore                          0x00000001066306e6 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
    26  QuartzCore                          0x0000000106630556 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
    27  QuartzCore                          0x000000010659c86e _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 242
    28  QuartzCore                          0x000000010659da22 _ZN2CA11Transaction6commitEv + 462
    29  UIKit                               0x00000001072d89ed -[UIApplication _reportMainSceneUpdateFinished:] + 44
    30  UIKit                               0x00000001072d96b1 -[UIApplication _runWithMainScene:transitionContext:completion:] + 2648
    31  UIKit                               0x00000001072d8095 -[UIApplication workspaceDidEndTransaction:] + 179
    32  FrontBoardServices                  0x000000010afb55e5 __31-[FBSSerialQueue performAsync:]_block_invoke_2 + 21
    33  CoreFoundation                      0x000000010696f41c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    34  CoreFoundation                      0x0000000106965165 __CFRunLoopDoBlocks + 341
    35  CoreFoundation                      0x0000000106964f25 __CFRunLoopRun + 2389
    36  CoreFoundation                      0x0000000106964366 CFRunLoopRunSpecific + 470
    37  UIKit                               0x00000001072d7b02 -[UIApplication _run] + 413
    38  UIKit                               0x00000001072da8c0 UIApplicationMain + 1282
    39  Chat App                            0x00000001054ca787 main + 135
    40  libdyld.dylib                       0x000000010925f145 start + 1
    41  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

这是 ChatsViewController 的代码：

class ChatsViewController: UIViewController, UITableViewDataSource 
@IBOutlet var chatsTable: UITableView!

var chats: [String] = []

override func viewDidLoad() 
    super.viewDidLoad()
    if PFUser.currentUser() == nil 
        println(1)
        let authVC: AuthenticationViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("auth") as! AuthenticationViewController // a custom class for the authentication view
        println(2)
        self.presentViewController(authVC, animated: true, completion: nil)
        println(3)
     else 
        chatsTable.dataSource = self
        chats = PFUser.currentUser()!.objectForKey("chats") as! [String]
    


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


func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
    return chats.count


func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell 
    let cell: ChatSessionCell = chatsTable.dequeueReusableCellWithIdentifier("ChatSessionCell", forIndexPath: indexPath) as! ChatSessionCell
    var chatID = chats[indexPath.row]
    var chat = getChatWithID(chatID)
    // TODO: put content in cell
    return cell


func getChatWithID(id: String) -> PFObject 
    var query = PFQuery(className: "Chat")
    query.whereKey("objectID", equalTo: id)
    let object: [PFObject] = query.findObjects() as! [PFObject] // should only be one object
    return object.first!


override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) 
    if segue.identifier == "toSession" 
        var sessionVC: SessionViewController = segue.destinationViewController as! SessionViewController
        sessionVC.sessionID = chats[chatsTable.indexPathForSelectedRow()!.row]
    

我已经搜索过这个错误，但似乎对于每种情况，原因和解决方案都不同。我该如何解决这个问题？

【问题讨论】：

您有当前用户吗？你确定数据源设置了吗？

当前没有用户，我试着打印出来，结果打印为零。此外，数据源在代码中设置（在 else 块中）并在情节提要中连接。

【参考方案1】：

已解决：我将 chatsTable.dataSource = self 移到 if 语句之前，这解决了问题。很可能它找不到 numberOfRowsInSection 方法，因为只有在存在 currentUser 时才设置 dataSource。

【参考方案2】：

您的视图控制器在 chats 实例化之前调用了 numberOfRowsInSection。

您应该将var chats: [String]! 替换为var chats = [String]()

【讨论】：

在到达chats.count之前发生错误。日志说找不到numberOfRowsInSection方法。