adapter-meta-programming.rb

module AdapterOne
  def instance_method
    ':one instance method'
  end
  alias one instance_method
end

module AdapterTwo
  def instance_method
    ':two instance method'
  end
  alias two instance_method
end

class Foo
  def initialize(adapter)
    case adapter
    when :one
      initialize_one
    when :two
      initialize_two
    end
  end

  attr_reader :adapter

  def initialize_one
    @adapter = :one
    extend AdapterOne
  end

  def initialize_two
    @adapter = :two
    extend AdapterTwo
  end
end

console.txt

> foo = Foo.new(:nope)
=> #<Foo:0x00007f9703905910>
> foo.respond_to?(:one)
=> false
> foo.respond_to?(:instance_method)
=> false
> foo1 = Foo.new(:one)
=> #<Foo:0x00007f970302b8a8 @adapter=:one>
> foo1.respond_to?(:one)
=> true
> foo1.respond_to?(:instance_method)
=> true
> foo1.instance_method
=> ":one instance method"
> foo2 = Foo.new(:two)
=> #<Foo:0x00007f9703824a78 @adapter=:two>
> foo2.respond_to?(:two)
=> true
> foo2.respond_to?(:instance_method)
=> true
> foo2.instance_method
=> ":two instance method"

debug.rb

foo = Foo.new(:nope)
foo.respond_to?(:one)
foo.respond_to?(:instance_method)

foo1 = Foo.new(:one)
foo1.respond_to?(:one)
foo1.respond_to?(:instance_method)
foo1.instance_method

foo2 = Foo.new(:two)
foo2.respond_to?(:two)
foo2.respond_to?(:instance_method)
foo2.instance_method