rails/activemodel/lib/active_model/naming.rb

require 'active_support/inflector'
require 'active_support/core_ext/hash/except'
require 'active_support/core_ext/module/introspection'

module ActiveModel
  class Name < String
    attr_reader :singular, :plural, :element, :collection, :partial_path, :route_key, :param_key, :i18n_key
    alias_method :cache_key, :collection

    def initialize(klass, namespace = nil)
      super(klass.name)
      @unnamespaced = self.sub(/^#{namespace.name}::/, '') if namespace

      @klass = klass
      @singular = _singularize(self).freeze
      @plural = ActiveSupport::Inflector.pluralize(@singular).freeze
      @element = ActiveSupport::Inflector.underscore(ActiveSupport::Inflector.demodulize(self)).freeze
      @human = ActiveSupport::Inflector.humanize(@element).freeze
      @collection = ActiveSupport::Inflector.tableize(self).freeze
      @partial_path = "#{@collection}/#{@element}".freeze
      @param_key = (namespace ? _singularize(@unnamespaced) : @singular).freeze
      @route_key = (namespace ? ActiveSupport::Inflector.pluralize(@param_key) : @plural).freeze
      @i18n_key = _singularize(self, '.').to_sym
    end

    # Transform the model name into a more humane format, using I18n. By default,
    # it will underscore then humanize the class name
    #
    #   BlogPost.model_name.human # => "Blog post"
    #
    # Specify +options+ with additional translating options.
    def human(options={})
      return @human unless @klass.respond_to?(:lookup_ancestors) &&
                           @klass.respond_to?(:i18n_scope)

      defaults = @klass.lookup_ancestors.map do |klass|
        klass.model_name.i18n_key
      end

      defaults << options[:default] if options[:default]
      defaults << @human

      options = {:scope => [@klass.i18n_scope, :models], :count => 1, :default => defaults}.merge(options.except(:default))
      I18n.translate(defaults.shift, options)
    end

    private

    def _singularize(string, replacement='_')
      ActiveSupport::Inflector.underscore(string).tr('/', replacement)
    end
  end

  # == Active Model Naming
  #
  # Creates a +model_name+ method on your object.
  #
  # To implement, just extend ActiveModel::Naming in your object:
  #
  #   class BookCover
  #     extend ActiveModel::Naming
  #   end
  #
  #   BookCover.model_name        # => "BookCover"
  #   BookCover.model_name.human  # => "Book cover"
  #
  #   BookCover.model_name.i18n_key              # => "book_cover"
  #   BookModule::BookCover.model_name.i18n_key  # => "book_module.book_cover"
  #
  # Providing the functionality that ActiveModel::Naming provides in your object
  # is required to pass the Active Model Lint test.  So either extending the provided
  # method below, or rolling your own is required..
  module Naming
    # Returns an ActiveModel::Name object for module. It can be
    # used to retrieve all kinds of naming-related information.
    def model_name
      @_model_name ||= begin
        namespace = self.parents.detect { |n| n.respond_to?(:_railtie) }
        ActiveModel::Name.new(self, namespace)
      end
    end

    # Returns the plural class name of a record or class. Examples:
    #
    #   ActiveModel::Naming.plural(post)             # => "posts"
    #   ActiveModel::Naming.plural(Highrise::Person) # => "highrise_people"
    def self.plural(record_or_class)
      model_name_from_record_or_class(record_or_class).plural
    end

    # Returns the singular class name of a record or class. Examples:
    #
    #   ActiveModel::Naming.singular(post)             # => "post"
    #   ActiveModel::Naming.singular(Highrise::Person) # => "highrise_person"
    def self.singular(record_or_class)
      model_name_from_record_or_class(record_or_class).singular
    end

    # Identifies whether the class name of a record or class is uncountable. Examples:
    #
    #   ActiveModel::Naming.uncountable?(Sheep) # => true
    #   ActiveModel::Naming.uncountable?(Post) => false
    def self.uncountable?(record_or_class)
      plural(record_or_class) == singular(record_or_class)
    end

    # Returns string to use while generating route names. It differs for
    # namespaced models regarding whether it's inside isolated engine.
    #
    # For isolated engine:
    # ActiveModel::Naming.route_key(Blog::Post) #=> posts
    #
    # For shared engine:
    # ActiveModel::Naming.route_key(Blog::Post) #=> blog_posts
    def self.route_key(record_or_class)
      model_name_from_record_or_class(record_or_class).route_key
    end

    # Returns string to use for params names. It differs for
    # namespaced models regarding whether it's inside isolated engine.
    #
    # For isolated engine:
    # ActiveModel::Naming.param_key(Blog::Post) #=> post
    #
    # For shared engine:
    # ActiveModel::Naming.param_key(Blog::Post) #=> blog_post
    def self.param_key(record_or_class)
      model_name_from_record_or_class(record_or_class).param_key
    end

    private
      def self.model_name_from_record_or_class(record_or_class)
        (record_or_class.is_a?(Class) ? record_or_class : convert_to_model(record_or_class).class).model_name
      end

      def self.convert_to_model(object)
        object.respond_to?(:to_model) ? object.to_model : object
      end
  end

end