Question

Today I think i might have learned something (not sure), i’m not really a obj-c programmer, more the php & java type, but building a iPhone app together with somebody got me this, so hopefully somebody can help me explain what and why:

I’ve put some code inside a @try {..} and @catch (NSException * e) {..} and my thought was everything would have been caught by that, but the other developer put and assert(false); at the end of the function, after de catch.

Why?

Answer 1

assert(3) is not part of Objective-C itself. It’s part of the C standard. Check out the man page. From the C spec, section 7.2.1.1 The assert macro:

Synopsis

    #include <assert.h>
    void assert(scalar expression);

Description

The assert macro puts diagnostic tests into programs; it expands to a void expression. When it is executed, if expression (which shall have a scalar type) is false (that is, compares equal to 0), the assert macro writes information about the particular call that failed (including the text of the argument, the name of the source file, the source line number, and the name of the enclosing function — the latter are respectively the values of the preprocessing macros __FILE__ and __LINE__ and of the identifier __func__) on the standard error stream in an implementation-defined format. It then calls the abort function.

So assert(false) will just crash the program at that point.