deprecate_method.rb(script)

This Ruby snippet employs the deprecate method defined within the Module class to mark other methods as deprecated. When this method is invoked with an existing method name, it dynamically creates a wrapper for that method. The wrapper issues a warning to standard error, signaling the deprecation of the original method, and then invokes the original method using aliasing to preserve its functionality. This allows developers to gradually phase out the usage of deprecated methods while providing a warning about their obsolescence. In the provided example, the mymethod of an instance of MyClass is marked as deprecated using the deprecate method, and attempting to call mymethod triggers a warning message.

Additionally, this snippet employs Ruby’s specialized features, often referred to as “Ruby metaprogramming” or “Ruby magic,” to open up and modify a class’s methods dynamically. This technique enables the alteration of existing class or module methods at runtime.

Ref. https://qiita.com/snaka/items/d3651b80cbca90a7956e

Execution:

class Module
  def deprecate(method_name)
      module_eval <<-END, __FILE__, __LINE__ + 1
        alias_method :deprecated_#{method_name}, :#{method_name}
        def #{method_name}(*args, &block)
          $stderr.puts "Warning: #{self}##{method_name} deprecate"
          deprecated_#{method_name}(*args, &block)
      end
    END
  end
end
#=> :deprecate

class MyClass
  def mymethod; end
  deprecate :mymethod
end
#=> :mymethod

MyClass.new.mymethod
#=> nil

Executed with Ruby 3.3.5