iPhone app running in Instruments fails with unrecognized selector

Question

I have an app that appears to run without problems in normal use. The Clang Static Analyzer reports no problems either. When I try to run it in Instruments, it fails with an unrecognized selector exception.

The offending line is a simple property setter of the form:

self.bar = baz;

To figure out what's going on, I added an NSLog() call immediately above it:

NSLog(@"class = %@ responds = %d", [self class], [self respondsToSelector:@selector(setBar:)]);
self.bar = baz;

On the emulator (without Instruments) and on a device, this shows exactly what I'd expect:

class = Foo responds = 1

When running under Instruments, I get:

class = Foo responds = 0

I'm stumped as to what could cause this. Perhaps a different memory location is getting tromped on when it's in the Instruments environment? Can anyone suggest how I might debug this?

Answer 1

If bar belongs to self, can't you do bar=baz; ?

Answer 2

Check your properties. Perhaps to you need a cast on baz?

Answer 3

There's not enough information here to know what's going on, but then, if you knew what information to provide you'd probably have already fixed it. So. A few things to check:

• Is the "self" pointer being swizzled in any way? Try printing out the value of self at various points just for sanity's sake
• When your code runs in Instruments, is it running in a different mode? (32-bit vs. 64-bit, Garbage collected vs. Retain-Release, etc.) I'm not sure why any of those would have an effect, but if it's running in a different mode, that's something to look into.
• Are you synthesizing the setter correctly? Or is it being provided dynamically (via Core Data, etc.)? If you manually specify a setBar: method, do you still get the error?