gistfile1.rb

class Feature < ActiveRecord::Base
    has_many :flat_features
    has_many :flats, through: :flat_features
end

class FlatFeature < ActiveRecord::Base
    belongs_to :flat
    belongs_to :feature
end

class Flat < ActiveRecord::Base
    has_many :flat_features
    has_many :features, through: :flat_features

    def full_feature_list()
        Feature.all.map { |feature| [feature, self.features.include? feature ] }
    end

    def has_feature(feature)
        self.features.include? feature
    end
end