class MyController < ApplicationController
  extend Sparkl::Decoration

  def_decorator :special_auth, before_action: [:auth, if: -> { true or false }]

  special_auth def show
    # ... normal controller logic here
  end

  # instead of:
  # before_action :auth, only: [:show], if: -> { true or false }
end

class MyController < ApplicationController
  extend Sparkl::Decoration

  def_decorator :no_auth, skip_before_action: :authorize
  def_decorator :verify_scope, after_action: ->() {
    # ... logic to check policy scoping...
  }

  verify_scope no_auth def show
    # ... normal controller logic here
  end

  # or with parentheses:
  # verify_scope(
  #   no_auth(
  #     def show
  #       # ... normal controller logic here
  #     end
  #   )
  # )
end

module MyActions
  extend Sparkl::Decorator

  def_decorator :redirect_if_true, before_action: [ :handle_redirect, { if: ->{ true } } ]

  private def handle_redirect
    redirect_to "..."
  end
end

class MyController < ApplicationController
  extend MyActions

  redirect_if_true def index
    # ...
  end
end

gem 'sparkl'

decorator :foo, before_action: ->{ puts 'foo' }, after_action: ->{ puts :bar }

decorator :foo, before_action: [:do_foo, if: :condition?]

# ...

# need to have do_foo and condition? methods defined
def do_foo
  # ...
end

def condition?
  true
end