Constant String vs. Immutable Strings

[jonthornham]

I thought constant strings and immutable strings were the same but after looking at Program 17.2 I am questioning myself.

If I create a string in the following ways what is the difference if any?

Code: (Objective-C)

NSString *myString1 = @"This is my string";
NSString *myString2 = [NSString stringWithString: @"This is also my string"];

Further more the note on page 411 says the system is clever and realizes the immutable string object is being initialized by a constant string object. What other objects can an immutable string be initialized with?

Thanks,

Jon

[skochan]

There really is no difference.   myString1 and myString2 will both reference a constant string object that has been created at compile time and that will have a reference count of 0xffffffff (or as noted in the text, on some systems, 0x7fffffff).

An immutable string object can be initialized from another immutable string object (either through a variable reference or constant string object) or from a mutable string object.

Cheers,

Steve Kochan

[jonthornham]

Thanks Steve.