iphone - NSObject 的 'description' 方法给出括号作为输出？

Question

因此，我正在调试正在构建的应用程序，并使用描述方法来帮助我找到问题。但它没有将应用程序作为字符串提供给我，而是打印出括号。请帮忙!

代码如下:

- (void)viewDidLoad {
[super viewDidLoad];

reminders = [[NSMutableArray alloc] init];
currentTitle = [[NSMutableString alloc] init];
currentDate = [[NSMutableString alloc] init];
currentSummary = [[
                NSMutableString alloc] init];
currentLink = [[NSMutableString alloc] init];

NSLog(@"IT'S HERE %@", [reminders description]);}

...

和错误:

[Session started at 2010-10-04 22:15:16 -0400.]
2010-10-04 22:15:17.434 Reminders[5824:207] ******* Accessibility Status Changed: On
2010-10-04 22:15:17.464 Reminders[5824:207] ********** Loading AX for: com.yourcompany.Reminders ************
2010-10-04 22:15:17.506 Reminders[5824:207] IT'S HERE (
)
2010-10-04 22:15:17.510 Reminders[5824:207] Hello
2010-10-04 22:15:17.512 Reminders[5824:207] (
)
2010-10-04 22:15:17.514 Reminders[5824:207] PVC: <UITableView: 0x602d600; frame = (0 20; 320 460); clipsToBounds = YES; opaque = NO; autoresize = W+H; layer = <CALayer: 0x5f3f3b0>; contentOffset: {0, 0}>
2010-10-04 22:15:17.514 Reminders[5824:207] It's here
2010-10-04 22:15:17.515 Reminders[5824:207] Loaded
2010-10-04 22:15:17.520 Reminders[5824:207] -[__NSCFArray name]: unrecognized selector sent to instance 0x6a4b640
2010-10-04 22:15:17.523 Reminders[5824:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFArray name]: unrecognized selector sent to instance 0x6a4b640'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x0248bb99 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x025db40e objc_exception_throw + 47
    2   CoreFoundation                      0x0248d6ab -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
    3   CoreFoundation                      0x023fd2b6 ___forwarding___ + 966
    4   CoreFoundation                      0x023fce72 _CF_forwarding_prep_0 + 50
    5   Reminders                           0x00003aa9 -[RootViewController tableView:cellForRowAtIndexPath:] + 300
    6   UIKit                               0x00090d6f -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 619
    7   UIKit                               0x00086e02 -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 75
    8   UIKit                               0x0009b774 -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1561
    9   UIKit                               0x000937ec -[UITableView layoutSubviews] + 242
    10  QuartzCore                          0x03f60481 -[CALayer layoutSublayers] + 177
    11  QuartzCore                          0x03f601b1 CALayerLayoutIfNeeded + 220
    12  QuartzCore                          0x03f592e0 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 302
    13  QuartzCore                          0x03f59040 _ZN2CA11Transaction6commitEv + 292
    14  UIKit                               0x0002204e -[UIApplication _reportAppLaunchFinished] + 39
    15  UIKit                               0x00022477 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 545
    16  UIKit                               0x0002c3ec -[UIApplication handleEvent:withNewEvent:] + 1958
    17  UIKit                               0x00024b3c -[UIApplication sendEvent:] + 71
    18  UIKit                               0x000299bf _UIApplicationHandleEvent + 7672
    19  GraphicsServices                    0x026fa822 PurpleEventCallback + 1550
    20  CoreFoundation                      0x0246cff4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
    21  CoreFoundation                      0x023cd807 __CFRunLoopDoSource1 + 215
    22  CoreFoundation                      0x023caa93 __CFRunLoopRun + 979
    23  CoreFoundation                      0x023ca350 CFRunLoopRunSpecific + 208
    24  CoreFoundation                      0x023ca271 CFRunLoopRunInMode + 97
    25  UIKit                               0x00021c6d -[UIApplication _run] + 625
    26  UIKit                               0x0002daf2 UIApplicationMain + 1160
    27  Reminders                           0x00002078 main + 102
    28  Reminders                           0x00002009 start + 53
)
terminate called after throwing an instance of 'NSException'

这是您向 Fluchtpunkt 请求的方法

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"cell";

    cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }

    // Configure the cell.

    Reminder *theReminder = [reminders objectAtIndex:indexPath.row];

    cell.textLabel.text = theReminder.name;

    return cell;

    }

Answer 1

如果我 NSLog 一个空数组，这些括号是我期望的输出。
这是绝对正确的。

<小时/>

引发异常是因为您尝试在 NS(Mutable)Array 上调用 name 方法。并且数组不响应名称。

要查找此异常的原因，请在 RootViewController 中发布此方法的代码

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath