iOS Debugging Crashes Finding information about a crash
Example
When your app crashes, Xcode will enter the debugger and show you more information about the crash:
The most important parts are:
The red arrow
The red arrow displays which line of code crashed & why it crashed.
The debugger console
Many crashes log more information to the debugger console. It should automatically appear when the app crashes, but if it's not there, show the debugger by selecting the 
button in the top-right corner of Xcode, and show the console by clicking the 
button in the bottom-right corner of the debugger.
The stack trace
The stack trace lists the functions the program came from before it got to the code that crashed.
Part of the stack trace is displayed in the Debug Navigator on the left of the screen, and the debugger controls allow you to select a stack frame to view in the debugger:
If you enter the bt command at the (lldb) prompt in the debugger and press return, you will get a textual representation of the stack trace that you can copy and paste:
(lldb) bt
* thread #1: tid = 0x3aaec5, 0x00007fff91055f06 libsystem_kernel.dylib`__pthread_kill + 10, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
frame #0: 0x00007fff91055f06 libsystem_kernel.dylib`__pthread_kill + 10
frame #1: 0x000000010008142d libsystem_pthread.dylib`pthread_kill + 90
frame #2: 0x00007fff96dc76e7 libsystem_c.dylib`abort + 129
frame #3: 0x00007fff8973bf81 libc++abi.dylib`abort_message + 257
frame #4: 0x00007fff89761a47 libc++abi.dylib`default_terminate_handler() + 267
frame #5: 0x00007fff94f636ae libobjc.A.dylib`_objc_terminate() + 103
frame #6: 0x00007fff8975f19e libc++abi.dylib`std::__terminate(void (*)()) + 8
frame #7: 0x00007fff8975ec12 libc++abi.dylib`__cxa_throw + 121
frame #8: 0x00007fff94f6108c libobjc.A.dylib`objc_exception_throw + 318
frame #9: 0x00007fff8d067372 CoreFoundation`-[__NSPlaceholderArray initWithObjects:count:] + 290
frame #10: 0x00007fff8d0eaa1f CoreFoundation`+[NSArray arrayWithObject:] + 47
* frame #11: 0x0000000100001b54 test`main(argc=1, argv=0x00007fff5fbff808) + 68 at main.m:15
frame #12: 0x00007fff8bea05ad libdyld.dylib`start + 1
frame #13: 0x00007fff8bea05ad libdyld.dylib`start + 1
