What is an actual example of the difference between NSString to NSMutablestring could look like?

Question

I'v been looking around in the questions here and could not find simple example to point me the difference while I was testing some code of my own to test the differentiation.

From what I understand, in an "immutable" string such as 'NSString', I could not preform any 'NSString' methods to modify the string, such as:

NSString *s = @"cat";

    s = [NSString stringWithString:@"blamp"];

    NSLog(@"%@", s);

But it does work..

Please try to give me and other newbies out there a very simple example of what won't work and why. tnx

Answer 1

The statement :

s = [NSString stringWithString:@"blamp"];

actually creates a new memory location for the string "blamp" and the old address of s gets replaced by this new address.

And you get the feel that the same s is updated!!! Actually the pointer now points to some other memory addresss.

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String manipulation means changing the same string : as if you try

NSString *s = @"cat";
[s appendString:@"s"];//tries to append to the same. this will through error.
//the above works with NSMutableString.