#define NSAssert(condition, desc)

Assertions evaluate a condition and, if the condition evaluates to false, 
call the assertion handler for the current thread, passing it a format 
string and a variable number of arguments. Each thread has its own assertion handler, 
which is an object of classNSAssertionHandler. When invoked, an assertion 
handler prints an error message that includes method and class names (or the function name). 
It then raises anNSInternalInconsistencyException exception.

This macro validates a parameter for an Objective-C method. Simply provide the
 parameter as the condition argument. The macro evaluates the parameter and, 
if it is false, it logs an error message that includes the parameter and then raises an exception.

Assertions are disabled if the preprocessor macro NS_BLOCK_ASSERTIONS is defined. 
All assertion macros return void.