学步园

int main(int argc, char *argv[])
{
    @autoreleasepool {
        // 异常停在了下面这行，毫无提示作用
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([MyClass class]));
    }
}

XCode的Console界面报出了一些出错信息, 如下图所示：

我根据Console里面的文字提示信息，猜出应该是出现了空指针nil的操作。但是具体出错在哪一行，却不知道。最终虽然找到了bug，但是debug的过程确实费了些时间。考虑到这个stace trace信息应该对我挺有帮助才对的，所以我就查了一下如何让这原本一堆16进制的调用栈信息更可读。于是在stackoverflow上找到了2个比较好的解决办法，在这里分享给大家。

方法一

该方法的步骤是，首先在你的AppDelegate中定义一个方法, 用于处理异常：

void uncaughtExceptionHandler(NSException *exception) {
    NSLog(@"CRASH: %@", exception);
    NSLog(@"Stack Trace: %@", [exception callStackSymbols]);
    // Internal error reporting
}

然后在应用启动时，设置这个方法作为自己的自定义异常回调：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSSetUncaughtExceptionHandler(&uncaughtExceptionHandler);
    // Normal launch stuff
}

Ape[2711:11303] CRASH: *** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[2]
Ape[2711:11303] Stack Trace: (
  0   CoreFoundation                      0x0209402e __exceptionPreprocess + 206
  1   libobjc.A.dylib                     0x01a71e7e objc_exception_throw + 44
  2   CoreFoundation                      0x0205aa95 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 165
  3   CoreFoundation                      0x020874e9 +[NSDictionary dictionaryWithObjects:forKeys:count:] + 73
  4   Ape                                 0x00096a0a +[QuestionParser parseToDictionary:] + 378
  5   Ape                                 0x00096434 -[QuestionStore putQuestion:] + 308
  6   Ape                                 0x00089ddf -[QuestionViewController requestFinished:] + 303
  7   Ape                                 0x000869dd -[NetworkAgent requestFinished:] + 653
  8   Ape                                 0x00085d33 __27-[NetworkAgent addRequest:]_block_invoke_0 + 131
  9   libdispatch.dylib                   0x01cf153f _dispatch_call_block_and_release + 15
  10  libdispatch.dylib                   0x01d03014 _dispatch_client_callout + 14
  11  libdispatch.dylib                   0x01cf2fd6 _dispatch_after_timer_callback + 28
  12  libdispatch.dylib                   0x01d03014 _dispatch_client_callout + 14
  13  libdispatch.dylib                   0x01cfa8b7 _dispatch_source_latch_and_call + 219
  14  libdispatch.dylib                   0x01cf6405 _dispatch_source_invoke + 322
  15  libdispatch.dylib                   0x01cf3768 _dispatch_main_queue_callback_4CF + 187
  16  CoreFoundation                      0x0203aaf5 __CFRunLoopRun + 1925
  17  CoreFoundation                      0x02039f44 CFRunLoopRunSpecific + 276
  18  CoreFoundation                      0x02039e1b CFRunLoopRunInMode + 123
  19  GraphicsServices                    0x0282b7e3 GSEventRunModal + 88
  20  GraphicsServices                    0x0282b668 GSEventRun + 104
  21  UIKit                               0x00be265c UIApplicationMain + 1211
  22  Ape                                 0x00016c5d main + 141
  23  Ape                                 0x00002b05 start + 53
  24  ???                                 0x00000001 0x0 + 1
)