iPhone SDK Tips & Tricks
NSMutableString *myString = [[NSMutableString alloc] initWithString:@”this and that”];
[myString replaceOccurencesOfString:@”this” withString:@”that” options:NSCaseInSensitiveSearch range:NSMakeRange(0, [myString length])];
NSLog(@"%@", myString);
or
myString = [myString stringByReplacingOccurrencesOfString:@"this"
withString:@"that"];