Ruby's super keyword

The super keyword in Ruby is used to invoke a method with the same name as the one currently being executed in the superclass. It allows us to extend or modify the behavior of a method defined in a superclass without completely overriding it. The super keyword is typically used within a subclass to call the superclass's implementation of the method.

Let's consider an example to understand the usage of the super keyword:

class Vehicle
  def start_engine
    puts "Engine started!"
  end
end

class Car < Vehicle
  def start_engine
    puts "Car started!"
    super
  end
end

my_car = Car.new
my_car.start_engine

In this example, we have a Vehicle class with a start_engine method. The Car class inherits from Vehicle and overrides the start_engine method. Within the overridden method in the Car class, we call super to invoke the superclass's implementation of start_engine. This allows us to extend the behavior while still retaining the original functionality.

When we execute the code, the output will be:

Car started!
Engine started!

Here, the start_engine method in the Car class prints "Car started!" and then calls super, which invokes the start_engine method in the Vehicle class. The superclass's implementation prints "Engine started!".

The super keyword can also take arguments when necessary. Let's consider another example:

class Animal
  def make_sound(sound)
    puts sound
  end
end

class Dog < Animal
  def make_sound(sound)
    puts "Bark!"
    super("Woof!")  # Passes "Woof!" as an argument to super
  end
end

my_dog = Dog.new
my_dog.make_sound("Woof woof!")

Output:

Bark!
Woof!

In this example, the make_sound method in the Dog class calls super("Woof!"), passing the argument "Woof!" to the make_sound method in the Animal class. The superclass's implementation prints "Woof!".

The super keyword is useful when we want to add behavior to a method while still utilizing the functionality provided by the superclass. It promotes code reuse and follows the principle of Don't Repeat Yourself (DRY).

Additionally, it's worth noting that the super keyword can be used without parentheses, like super or with parentheses, like super(). The choice depends on whether arguments need to be passed to the superclass method.