Parmanoir

When failing, functions like NSXMLDocument's initWithContentsOfURL:options:error: give more information via NSError than a BOOL. And you end up with code looking like that …

// Log and return 
if (error)
{
	// Somehow display the error
	NSLog(@"MyFunction failed with error: %@", error);
	// And return from our function
	return NO;
}

… opening a brace just to handle the error. This can be compacted with :

// Log and return 
if (error)	return NSLog(@"MyFunction failed with error: %@", error), NO;

The comma operator evaluates expressions (standard arithmetic, function calls, etc. but NOT statements : while, if, …) and returns the value of the last one.

• 1, 2, 3 yields 3
• fn(), NO calls fn and yields NO
• fn1(), fn2(), fn3() calls fn1, then fn2, then fn3, then yields the result of fn3

return will evaluate its following expression (the comma-separated expression list) and return the value of the last one. This allows you to do one quick call to some logging function before returning.

I used to do that in Javascript for logging, it's nice to see it also fits nicely in ObjC. Not that you should pack function calls on your returns (return fn1(), fn2(), fn3(), fn4(), fn5() will work ! ) but I think it's a nice thing to know.