Question

Can you please explain me exact difference between these two lines?

NSArray *foo = [NSArray arrayWithObjects:@"hai",@"how",@"are",@"you",nil];
NSArray *bar = [[NSArray alloc] initWithObjects:@"hai",@"how",@"are",@"you",nil];

Answer 1

arrayWithObjects is “convenience constructor”.

It will do:

return [[[NSArray alloc] initWithObjects:@"hai",@"how",@"are",@"you",nil] autorelease]

for you.

It is just a convenience method to get an autoreleased object while improving the readability of the statement. Keep in mind that the fact that the object is autoreleased is a simple convention of the language (not a rule, so you could do differently, but I would not suggest that).