objective-c - 如何确定哪个 NSNotification 由于 dealloc-ed 观察者而崩溃

Question

使用NSNotification的黄金法则似乎是

"call removeObserver before the observer (or the object) is deallocated".

我正在处理未遵循此规则的代码库，但我找不到违规行为。我搜索了代码并确保每个 addObserver 都有匹配的 removeObserver 但我仍然看到以下各种崩溃报告:

OS Version:      iPhone OS 5.0.1 (9A405)
Report Version:  104

Exception Type:  SIGSEGV
Exception Codes: SEGV_ACCERR at 0x8
Crashed Thread:  0

Thread 0 Crashed:
0   libobjc.A.dylib                     0x31516fbc objc_msgSend + 16
1   Foundation                          0x3195b50f __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_0 + 19
2   CoreFoundation                      0x37a02577 ___CFXNotificationPost_block_invoke_0 + 71
3   CoreFoundation                      0x3798e0cf _CFXNotificationPost + 1407
4   Foundation                          0x318cf3fb -[NSNotificationCenter postNotificationName:object:userInfo:] + 67
5   UIKit                               0x34e5ee25 -[UIApplication _handleApplicationSuspend:eventInfo:] + 697
6   UIKit                               0x34deed17 -[UIApplication handleEvent:withNewEvent:] + 2031
7   UIKit                               0x34dee3bf -[UIApplication sendEvent:] + 55
8   UIKit                               0x34dedd2d _UIApplicationHandleEvent + 5809
9   GraphicsServices                    0x3750bdf3 PurpleEventCallback + 883
10  CoreFoundation                      0x37a0a553 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 39
11  CoreFoundation                      0x37a0a4f5 __CFRunLoopDoSource1 + 141
12  CoreFoundation                      0x37a09343 __CFRunLoopRun + 1371
13  CoreFoundation                      0x3798c4dd CFRunLoopRunSpecific + 301
14  CoreFoundation                      0x3798c3a5 CFRunLoopRunInMode + 105
15  GraphicsServices                    0x3750afcd GSEventRunModal + 157
16  UIKit                               0x34e1c743 UIApplicationMain + 1091
17  App                                 0x00002d2f main (main.m:14)

我对这个崩溃报告的解释是，[UIApplication _handleApplicationSuspend:eventInfo:] 发布了一个通知，观察者在被删除之前已经被释放。

假设这种解释是正确的，我将如何确定发布的通知？理想情况下，释放的对象类型是什么？

Answer 1

你可以在 -[NSNotificationCenter postNotificationName:object:userInfo:] 中设置一个符号断点并打印传递给它的第三个参数(第一个是 NSNotificationCenter，第二，_cmd) 使用调试器 po 命令。