NSMutableAttributedString的问题

Question

我们目前正在对一个新的应用程序进行beta测试，在这个测试中我遇到了一些我不理解的崩溃。这不会在我的设备或模拟器上发生，但在我们部署进行测试的现场的一些设备上确实会崩溃。与此相关的代码如下：

@implementation NSMutableAttributedString (Helper)

-(NSRange)appendString:(NSString *)string withAttributes:(NSDictionary *)attributes {

     if (![self respondsToSelector:@selector(length)]) {
         DDLogError(@"SELF can't respond to length selector. Wonder what is going on here... \n%@", [NSThread callStackSymbols]);
         DDLogError(@"SELF is of type %@", [self class]);
     }

     NSUInteger loc = self.length;
     if (string == nil) return NSMakeRange(loc, 0);

     if (![string isKindOfClass:[NSString class]]) {
         DDLogError(@"Got a non string in my appendString function.  Wonder what is going on here... \n%@", [NSThread callStackSymbols]);
         DDLogError(@"string is of type %@", [string class]);
         return NSMakeRange(loc, 0);
     }




     [self.mutableString appendString:string];
     NSRange ret = NSMakeRange(loc, string.length);
     if (attributes != nil) [self addAttributes:attributes range:ret];
     return ret;
}

-(NSRange)appendString:(NSString *)string {    
     return [self appendString:string withAttributes:nil]; // THIS IS LINE 40!
}
@end

崩溃日志如下所示：

Incident Identifier: F9945D73-60D1-438D-B2CE-76634A501D69
CrashReporter Key:   91DBE709-85A2-4F9E-AF82-6D7C0248F443
Hardware Model:      iPhone3,1
Process:         HDScores [152]
Path:            /Users/USER/HDScores.app/HDScores
Identifier:      com.hdscores.consumer.service.clients.ios
Version:         1.23
Code Type:       ARM
Parent Process:  launchd [1]

Date/Time:       2014-07-16T19:56:43Z
OS Version:      iPhone OS 7.1.2 (11D257)
Report Version:  104

Exception Type:  SIGSEGV
Exception Codes: SEGV_ACCERR at 0x6570706d
Crashed Thread:  0

Application Specific Information:
objc_msgSend() selector name: length

Thread 0 Crashed:
0   libobjc.A.dylib                      0x3a33d626 objc_msgSend + 6
1   TextToSpeech                         0x374a0431 TTSCopyModificationDateForFileAtURL + 1610
2   HDScores                             0x00030935 -[NSMutableAttributedString(Helper) appendString:] (NSMutableAttributedString+Helper.m:40)
3   HDScores                             0x00037fe7 -[EstablishmentDetailViewController viewDidLoad] (EstablishmentDetailViewController.m:170)
4   UIKit                                0x323a44ab -[UIViewController loadViewIfRequired] + 516
5   UIKit                                0x3244ebe1 -[UINavigationController _layoutViewController:] + 30
6   UIKit                                0x3244eaf7 -[UINavigationController _updateScrollViewFromViewController:toViewController:] + 228
7   UIKit                                0x3244e0d3 -[UINavigationController _startTransition:fromViewController:toViewController:] + 76
8   UIKit                                0x3244ddfd -[UINavigationController _startDeferredTransitionIfNeeded:] + 570
9   UIKit                                0x3244db6d -[UINavigationController __viewWillLayoutSubviews] + 42
10  UIKit                                0x3244db05 -[UILayoutContainerView layoutSubviews] + 182
11  UIKit                                0x025d1ab3 0x2580000 + 334515
12  UIKit                                0x3239fd59 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 378
13  QuartzCore                           0x3201d62b -[CALayer layoutSublayers] + 140
14  QuartzCore                           0x32018e3b CA::Layer::layout_if_needed(CA::Transaction*) + 348
15  QuartzCore                           0x32018ccd CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 14
16  QuartzCore                           0x320186df CA::Context::commit_transaction(CA::Transaction*) + 228
17  QuartzCore                           0x320184ef CA::Transaction::commit() + 312
18  QuartzCore                           0x3201221d CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 54
19  CoreFoundation                       0x2fb4e255 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 18
20  CoreFoundation                       0x2fb4bbf9 __CFRunLoopDoObservers + 282
21  CoreFoundation                       0x2fb4bf3b __CFRunLoopRun + 728
22  CoreFoundation                       0x2fab6ebf CFRunLoopRunSpecific + 520
23  CoreFoundation                       0x2fab6ca3 CFRunLoopRunInMode + 104
24  GraphicsServices                     0x349bc663 GSEventRunModal + 136
25  UIKit                                0x3240314d UIApplicationMain + 1134
26  HDScores                             0x0003daab main (main.m:17)
27  libdyld.dylib                        0x3a840ab7 start + 0

有谁有什么想法吗？我可以告诉您，DDLogError语句永远不会命中，作为尝试诊断问题的最后一搏而抛出。它看起来像是在发送一个错误，因为长度不是一个已知的选择器。同样，这只出现在iPhones上，而不是具有相同代码的iPads上。到目前为止，只有几个iPhones (一个是5，一个是4)，都在iOS7上。

Answer 1

简单地说，我能够解决这个问题的方法是重命名了我的帮助器函数(例如，它们现在被命名为helperAppendString withAttributes等)。出于某种原因，这解决了这个问题。从日志中看，它似乎是在调用其他对象实例，而不是self appendString withAttributes……

听起来很疯狂，但是当我重命名这些函数时，这个问题已经消失了。