shvets / design_patterns_in_ruby

# factory-method.rb
 
# Defines an interface for creating an object, but let subclasses decide which
# class to instantiate. Lets a class to defer instantiation to sublcasses.
 
# 1. common type interface
 
class Shape 
  def draw
  end
end
 
# 2. implementations of common type interface
 
class Line < Shape 
  def draw
    puts "line"
  end
end
 
class Square < Shape 
  def draw
    puts "square"
  end
end                             
 
# 3. Creator class for various types
 
class ShapeCreator 
 
  # factory methods
 
  def create_line
    Line.new
  end
 
  def create_square
    Square.new
  end
 
  # or universal factory method (parameterized factory method)
 
  def create_shape(type) 
    if(type == :line) 
      Line.new
    elsif(type== :square) 
      Square.new
    end
  end
 
end
 
# 4. test
 
shape_creator = ShapeCreator.new
 
shape1 = shape_creator.create_line
shape2 = shape_creator.create_square
shape3 = shape_creator.create_shape :line
 
shape1.draw
shape2.draw
shape3.draw