hangoff active record plugin

gistfile1.rb

      def with_hangoff_table(relation_name, opts={})

        hangoff_table = reflections[relation_name].table_name
        foreign_key = reflections[relation_name].foreign_key
        name_column = opts[:name_column] || :attribute_name
        value_column = opts[:value_column] || :attribute_value

        (class << self; self; end).send(:define_method, relation_name) do |params|
        table_alias = hangoff_table + SecureRandom.hex(4)
        join_string = "INNER JOIN #{hangoff_table} AS #{table_alias} ON #{table_alias}.#{foreign_key} = #{table_name}.#{primary_key}"
        scoped.joins(join_string).where(params.inject({}) do |hash, vals|
          hash["#{table_alias}.#{name_column}"] = vals[0]
          hash["#{table_alias}.#{value_column}"] = vals[1]
          hash
        end)
        end
      end

in model

has_many :drug_categories, foreign_key: :drug_name_report_id
with_hangoff_table :drug_categories, name_column: :category_name, value_column: :category_value


#Now you have a class method named after the relation where you can pass a "where" style hash of params to query the hangoff table as if it had columns

MyModel.drug_categories(drug_type: 'biomedical')

#drug type is actually a value in drug_categories underlying table in the :category_name column and 'biomedical' is in the same row in the :category_value column