Working Book Example App - Rent Action with custom precondition

availability.rb

# frozen_string_literal: true

class Ba::Book::Availability < Granite::Action::Precondition
  description 'Must not be available to rent'

  def call(**)
    decline_with(:unavailable) unless book_available?
  end

  private

  def book_available?
    book.available?
  end
end

rent.rb

# frozen_string_literal: true

class Ba::Book::Rent < BaseAction
  allow_if { performer.is_a?(User) }

  projector :inline

  subject :book

  precondition Availability

  private

  def execute_perform!(*)
    subject.available = false
    subject.save!
    ::Rental.create!(book: subject, user: performer)
  end
end