How to reduce code duplication

By using Ruby or Pyton you might know about the fact that both are dynamically typed, as a result a developer can choose some of the variants available to remove some of the duplication. There are at least 2 methods that can be used to reduce code duplication.

Dynamic declaration:

class MyClass
  STATUS_ARRAY = [ :pending, :closed, :rejected, :waiting_for_payment ]
  STATUS_ARRAY.each do |method|
    class_eval %{
      scope :#{method}, where('column_name = ?', #{method.to_sym}) 
      def #{method}?
        self[:column_name] == '#{method}'
      end
      alias :is_#{method}?, #{method}?
    }
  end
end

In the example above we managed to write 8 lines that compress the code by declaring dynamically the equivalent of a 20 lines.

Inheritance

In Ruby you can easily use modules that you can include into your classes or you could use extend.

The below example you might encounter in all the Rails application upon class definitions, but this method is somehow limiting as you cannot extend with more than 1 class. In the below example we are extending the Foo class from Class1. Better said, Class1 is an ancestor of Foo

class Foo < Class1
end

However you could also use multiple inheritance by using the following example:

class Foo
  extend Class1
  extend Class2
end

The above example allows you to use several classes as a parent for Foo, however this might not be the best approach, because defies some OOP principles. As a workaround, is better to use modules.

Modules usage

class Foo < Class1
  include Module1 
  include Module2
end

I have shown here how to create a module

Alecslupu