concatstring.m

NSString *string1 = @"This is";
NSString *string2 = @" a test.";
NSString *string3 = [string1 stringByAppendingString:string2];
// string3 is now @"This is a test."  string1 and string2 are unchanged.

//You can also assign the new string back to string1:

NSString *string1 = @"This is";
NSString *string2 = @" a test.";
string1 = [string1 stringByAppendingString:string2];
// string1 is now @"This is a test."

//If you're using a NSMutableString, you can simply call the appendString method:

NSMutableString *string1 = [NSMutableString stringWithString:@"This is"];
NSString *string2 = @" a test.";
[string1 appendString:string2];
NSLog(@"string1: %@", string1);