String replacement in Objective-C

What is the best way to replace a character is a string in Objective-C for iPhone SDK?

From stackoverflow

• NSString objects are immutable (they can't be changed), but there is a mutable subclass, NSMutableString, that gives you several methods for replacing characters within a string. It's probably your best bet.

• You could use the method

  - (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target 
                                          withString:(NSString *)replacement
  

  ...to get a new string with a substring replaced (See NSString documentation for others)

  Example use

  NSString *str = @"This is a string";
  
  str = [str stringByReplacingOccurrencesOfString:@"string"
                                       withString:@"duck"];