NSMutableAttributedString的问题

Question

We are currently in beta testing of a new app where i am getting some crashes that i don't understand. It doesn't happen on my device or simulator, but does crash on a few devices in the field we have deployed for testing. The code related to this is:

@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

The crash log looks like:

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

Anyone have any ideas? I can tell you the DDLogError statements are never hit, thrown in as a last ditch to try to diagnose the issue. It looks like it is sending an error because length is not a known selector. Again, this appears only on iPhones, not iPads with the same code. and so far, only a few iPhones (one is a 5, one is a 4), all on IOS 7. Any help, i'm pulling my hair out on this one...

Answer 1

Just to put this out there, the way i was able to fix the issue is i renamed my helper functions (for example, they are now named helperAppendString withAttributes etc...). For some reason, this fixed the issue. From the log, it looked like it was calling some other object instance instead of the [self appendString withAttributes]...

Sounds crazy, but the issue has gone away when i renamed the functions.