StringWithFormat vs initWithFormat under ARC

Question

stringWithFormat: is a method of the NSString class and returns a string with auto-implementation; initWithFormat: is an instance method, and before ARC, the programmer had to take care of managing the memory of the returned object. If we included ARC, what is the difference between the two methods?

Answer 1

With ARC, these two methods are equivalent.

See:

• WWDC 2011 Session Video - Introduction of an Automatic Directory Counting
• WWDC 2011 Session Video - Objective-C In-Depth Promotion (explains how ARC code is compiled)

Answer 2

If ARC is enabled, there should be no difference.

Usually you call initWithFormat: after you have allocated your NSString, so the count without ARC will be 1 more than if you used the auto-implemented class method to create your own string (this way, you should free it).

There is no difference with ARC, because save / release / auto-detection is fully processed for you.