There's a bug in my app which shows up with the following (partial) stacktrace:
2011-11-25 01:55:59.760 Events2[6650:403] -[Event boolValue]: unrecognized selector sent to instance 0x7fb903928670
To debug this I decided to add a symbolic breakpoint on -[Event boolValue] reasoning that when that selector is sent, the debugger would halt.
However, nothing happens. After setting the breakpoint the app just soldiers on and generates the same exception without halting.
I have defined the breakpoint as follows:
I'm using the LLDB debugger with Xcode 4.2
Setting a breakpoint on a selector causes lldb to halt when that selector is executed, not when it is sent. In your case, there is no selector "-[Event boolValue]", therefore this breakpoint will never be hit.
I would set an exception breakpoint on "All Objective-C Exceptions". This will be hit when the "unrecognized selector sent" exception is thrown and you can see where the problem occurs.
I was looking for the same answer (symbolic breakpoints) and this link helped: http://www.cocoabuilder.com/archive/cocoa/308967-symbolic-breakpoints.html#308970
You have to follow this pattern (it is also given as a placeholder in Xcode breakpoint editor):
- [name_of_the_class name_of_the_method:]
For example I was looking to see who does set my left bar item and overrides my settings, I used
-[UINavigationItem setLeftBarButtonItem:]
and it worked. Or this one
-[UINavigationController pushViewController:animated:]
I would set an Symbolic breakpoint with this symbol -[NSObject doesNotRecognizeSelector:]
which will help us to capture situations where a selector is being invoked against the wrong object.
It looks to me like symbolic breakpoints don't work right in LLDB (I'm running the most recent released version of Xcode as of this writing, 4.3.3).
I set a symbolic breakpoint at addAnimation:forKey: in LLDB, and it never gets hit. If I switch my project to GDB, the breakpoint works as expected.
Best way to find unrecognized selector call is to create this selector (as category) and put a break point in it.
来源：https://stackoverflow.com/questions/8264193/add-a-symbolic-breakpoint-on-a-selector-in-xcode