EXC_BAD_ACCESS...What is it and what is it doing in my program?

Question

As a basic exercise, I was working on this function:
void PrintIntrospectionInfo () // function definition for section 4
// code for printing "introspection info"
NSString *s1 = [NSString stringWithString: @"Assignment"];
NSString *s2 = [NSString stringWithString: @"hello world!"];
NSURL *u1 = [NSURL URLWithString: @"http://www.apple.com"];
NSURL *u2 = [NSURL URLWithString: @"http://192.168.0.197"];
NSMutableString *ms1 = [NSMutableString stringWithString: @"Assignment 1"];
// NSMutableString *ms2 = [ms1 appendString: @"B"];
NSDictionary *d1 = [NSDictionary dictionaryWithObjectsAndKeys: u1, s1, u2, s2, nil];
NSMutableArray *array = [NSMutableArray arrayWithObjects: s1, s2, u1, u2, ms1, d1, nil];
SEL selector = @selector (lowercaseString:);
for (id object in array)
NSLog (@"Class name: %@", [object className]);
NSLog (@"Is member of NSString: %@", [object isMemberOfClass: [NSString class]]);
NSLog (@"Is kind of NSString: %@", [object isKindOfClass: [NSString class]]);
NSLog (@"Responds to lowercaseString: %@", [object respondsToSelector: selector]);
if ([object respondsToSelector: selector])
NSLog (@"lowercaseString is: %@", [object performSelector: selector]);
On the first iteration of the for() loop, the second NSLog returns an EXCBADACCESS in the debugger. What is EXCBADACCESS, and why is it showing up in my program?

Answer 1

musicwind95 wrote:
I thought %@ was a sort of (id) format specifier
It is, but BOOL isn't an id, it is just an int.
so what is the format specifier for a BOOL value?
You can use %d, but if you want to be more clever, you can keep it as %@ but use a value of:
(value ? @"YES" : @"NO")