CODESAMPLE

Adapter - Ruby

Adapter Ruby

The Adapter pattern converts the interface of a class into another interface clients expect. This allows classes with incompatible interfaces to collaborate. Our example adapts a LegacyRectangle class with a different area calculation method to the GeometricShape interface which requires a standardized area method. We achieve this with an RectangleAdapter class that wraps the LegacyRectangle and provides the required area method, calling the legacy class’s method internally. This implementation leans into Ruby’s duck typing, where method calls are executed if an object responds to them, rather than strict interface enforcement.

# GeometricShape interface
module GeometricShape
  def area
    raise NotImplementedError
  end
end

# Legacy class with incompatible interface
class LegacyRectangle
  attr_reader :width, :height

  def initialize(width, height)
    @width = width
    @height = height
  end

  def calculate_area
    @width * @height
  end
end

# Adapter class
class RectangleAdapter
  include GeometricShape

  def initialize(legacy_rectangle)
    @legacy_rectangle = legacy_rectangle
  end

  def area
    @legacy_rectangle.calculate_area
  end
end

# Client code
legacy_rect = LegacyRectangle.new(5, 10)
adapter = RectangleAdapter.new(legacy_rect)

puts "Area of legacy rectangle (via adapter): #{adapter.area}"

# Example using another object that directly implements GeometricShape
class Square
  include GeometricShape

  def initialize(side)
    @side = side
  end

  def area
    @side * @side
  end
end

square = Square.new(4)
puts "Area of square: #{square.area}"