The final word on NSStrings: Mutable and Immutable

Question

I\'ve read in several books... and online... about immutable and mutable strings. They claim \"immutable strings\" can\'t be changed. (But they never define \"change\".)

Answer 1

If I declare a variable:

NSString * var;
// Here some code giving a new value to var

What is immutable is the object pointed to by var, not var itself.

This means that I cannot change anything of the object pointed to by var, but I can change which object is pointed to.

None of the operations you mention is allowed on var, but you can assign var with another different string:

NSString * anotherVar;
// Here some code giving a new value to anotherVar

var = anotherVar; // This is allowed (with a memory leak if GC is disabled)

// The following is also allowed: -stringWithFormat: creates a new object
var = [var stringWithFormat:@"%@ with more chars", var];