In Objective-C, you can concatenate two strings together using the stringByAppendingString: method. Here is an example:
``objective-c
NSString *str1 = @"Hello ";
NSString *str2 = @"World!";
NSString *result = [str1 stringByAppendingString:str2];
NSLog(@"%@", result); // Output: "Hello World!"
In the above example, we have created two strings and str2 and concatenated them using the stringByAppendingString: method. This method returns a new string with the second string appended to the first string.
You can also use the stringWithFormat: method to concatenate strings. Here is an example:
objective-c
NSString *firstName = @"John";
NSString *lastName = @"Doe";
NSString *fullName = [NSString stringWithFormat:@"%@ %@", firstName, lastName];
NSLog(@"%@", fullName); // Output: "John Doe"
`
In the above example, we have used the stringWithFormat: method to concatenate two strings firstName and lastName into a single string fullName. We have passed the %@` format specifier to indicate that we want to insert a string value at that position.