Prepend module to avoid monkey patching classes

Imagine this class

class Point
  def to_s
    puts "Point (X1,Y1)"    
  end  
end

Point.new.to_s
#=> Point (X1,Y1)

Imagine a child class that inherits from parent class Point

class SpecialPoint < Point
  def to_s
    puts "Special "
    super
  end
end 

puts SpecialPoint.new.to_s
#=> Special
#=> Point (X1,Y1)

Point & SpecialPoint are not accessible, like in a gem.

Imagine you want to customize the to_s ooutput. You can do the following.

module Extra
  def to_s
    puts "Extra must be the first comment "
    super
  end
end

Including the module is not working as desired

SpecialPoint.send(:include, Extra)
puts SpecialPoint.new.to_s
=> Special
=> Extra must be the first comment
=> Point (X1,Y1)

Prepend comes to the rescue!

SpecialPoint.send(:prepend, Extra)
puts SpecialPoint.new.to_s
=> Extra must be the first comment
=> Special
=> Point (X1,Y1)