lib/active_relation/relations/rename.rb


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module ActiveRelation
  class Rename < Compound
    attr_reader :attribute, :pseudonym

    def initialize(relation, pseudonyms)
      @attribute, @pseudonym = pseudonyms.shift
      @relation = pseudonyms.empty?? relation : Rename.new(relation, pseudonyms)
    end

    def ==(other)
      self.class == other.class and relation == other.relation and attribute == other.attribute and pseudonym == other.pseudonym
    end

    def qualify
      Rename.new(relation.qualify, attribute.qualify => pseudonym)
    end
    
    def attributes
      relation.attributes.collect(&method(:substitute))
    end
    
    protected
    def attribute_for_name(name)
      case
      when referring_by_autonym?(name) then nil
      when referring_by_pseudonym?(name) then substitute(relation[attribute])
      else relation[name].substitute(self) rescue nil
      end
    end

    private
    def substitute(attribute)
      (attribute =~ self.attribute ? attribute.as(pseudonym) : attribute).substitute(self) rescue nil
    end

    def referring_by_autonym?(name)
      relation[name] == relation[attribute]
    end
    
    def referring_by_pseudonym?(name)
      name == pseudonym
    end
  end
end