README.md

Shortcut to prepend module that checks an argument and only calls original implementation if argument evals to false. Other versions could instead execute super(*args) and do different things depending on the result.

my_class.rb

class MyClass
  extend Prependable
  
  define_prepend :dry, guard: -> { dry_run? }, body: ->(name) { puts "#{name} was called." }

  dry def delete
    MyFileUtil.copy_to_trash
    MyFileUtil.delete_all
  end
  
  dry def move
    MyFileUtil.copy_to_loclation
    MyFileUtil.delete_all
  end
  
  private
  
  def dry_run?
    ENV["dry"]
  end
end

prependable.rb

# frozen_string_literal: true

module Prependable
  def define_prepend(prepend_name, guard:, body:)
    define_singleton_method(prepend_name) do |name|
      mod = Module.new do
        define_method(name) do |*args|
          if instance_exec(&guard)
            instance_exec(name, &body)
          else
            super(*args)
          end
        end
      end

      prepend mod
      name
    end
  end
end