Bad access exception on attempt to strlen a C string in Objective C on iOS

Question

Second line throws an EXC_BAD_ACCESS exception. I'm not too familiar with Objective C or C, but an SDK I'm using takes C parameters. What am I doing wrong here?

unsigned char *header = (unsigned char*)[
    [ticket_design objectForKey:@"header"]
    cStringUsingEncoding:NSStringEncodingConversionAllowLossy
];
int header_length = strlen((const char*)header);

Answer 1

If possible, I would just go the standard route by making header an NSString and then:

int len = [myString length];

I think this would prevent the ugly crash... but it seems like header is empty or not null terminated.