В Ruby существует несколько способов объединения строк. Вот несколько методов и примеры кода:

1. Использование оператора +:

   first_name = "John"
   last_name = "Doe"
   full_name = first_name + " " + last_name
   puts full_name # Output: "John Doe"

2. Использование оператора <<:

   first_name = "John"
   last_name = "Doe"
   full_name = first_name << " " << last_name
   puts full_name # Output: "John Doe"

3. Использование метода concat:

   first_name = "John"
   last_name = "Doe"
   full_name = first_name.concat(" ", last_name)
   puts full_name # Output: "John Doe"

4. Использование строковой интерполяции #{}:

   first_name = "John"
   last_name = "Doe"
   full_name = "#{first_name} #{last_name}"
   puts full_name # Output: "John Doe"

5. Использование метода join:

   name_parts = ["John", "Doe"]
   full_name = name_parts.join(" ")
   puts full_name # Output: "John Doe"

6. Использование метода concatenate:

   first_name = "John"
   last_name = "Doe"
   full_name = [first_name, last_name].join(" ")
   puts full_name # Output: "John Doe"