karolkozub / kkassert

Objective-C assertion macro

KKAssert

I created KKAssert because I was annoyed by the limitations of NSAssert and assert. Within my implementation I tried to use the best parts from both of these solutions. I'm pretty happy with the results.

What is wrong with NSAssert?

• It requires at least two arguments. My assertions are usually very simple and don't require any additional descriptions. The fact that I have to supply an empty second argument every single time is very irritating.
• It doesn't log the stringized condition, which is a pretty handy information.
• It doesn't work in functions. There is the alternative NSCAssert macro, but it is more convenient not to have to remember that.

What is wrong with assert?

• It doesn't provide stacktraces. When something fails I need a stacktrace to debug the problem. It is the single most useful information an assertion can provide. Since assert just logs its message and calls abort(), there is nothing except for some information about the last frame.
• It doesn't allow you to specify a custom description. Most of the time a description isn't needed, but it's useful to have that possibility for the rare case when it's needed.
• It logs method calls as functions (e.g. function -[Xyz xyz]), which is a bit annoying. It also uses __FUNCTION__ instead of the more verbose __PRETTY_FUCTION__

How does KKAssert handle these things?

• It allows you to specify only one argument -- the condition. Since most of the time a custom description isn't needed, the tab completion will suggest a single argument as well.
• It logs the stringized condition in its message. The logged part is very similar to the assert's one.
• It works both in methods and in functions.
• It provides a stacktrace by raising an exception. The same way NSAssert does it. When you don't specify a custom description the exception will use the logged message in its place.

How to use KKAssert?

#import "KKAssert.h"

void test(int argument) {
  KKAssert(argument > 10);
  
  (...)  
}

@implementation KKCustomView

- (void)animateWithObject:(id)object {
  KKAssert([NSThread isMainThread]);
  KKAssert([object isPreparedForAnimation], @"Object %@ wasn't ready for animation", object);
  
  (...)
}

@end

What does the failure message look like?

@implementation Test
- (void)test {
	KKAssert(1 == 2);
}
@end

2014-04-23 02:46:36.148 Untitled 10[41961:507] *** Assertion failed: (1 == 2), -[Test test], file Untitled 10.m, line 36
2014-04-23 02:46:36.151 Untitled 10[41961:507] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Assertion failed: (1 == 2), -[Test test], file Untitled 10.m, line 36'
*** First throw call stack:
(
	0   CoreFoundation                      0x00007fff8353525c __exceptionPreprocess + 172
	1   libobjc.A.dylib                     0x00007fff8cae6e75 objc_exception_throw + 43
	2   CoreFoundation                      0x00007fff8353510c +[NSException raise:format:] + 204
	3   Untitled 10                         0x0000000107682dbf -[Test test] + 175
	4   Untitled 10                         0x0000000107682e90 main + 64
	5   libdyld.dylib                       0x00007fff886d35fd start + 1
	6   ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Run Command: line 1: 41961 Abort trap: 6           ./"$2" "${@:3}"