Module: Unpolymorph

Defined in:
lib/unpolymorph.rb,
lib/unpolymorph/version.rb

Constant Summary collapse

VERSION = 
"0.1.2"

Instance Method Summary collapse

Instance Method Details

#unpolymorph(name, associations) ⇒ Object 



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# File 'lib/unpolymorph.rb', line 5

def unpolymorph( name, associations )

  scope "for_#{name}", -> obj { where( "#{obj.class.base_class.to_s.underscore}_id" => obj.id ) }

  define_method( name ) do
    associations.each do |assoc|
      associated = send( assoc )
      return associated if associated
    end
  end

  define_method( "#{name}=" ) do |value|
    associations.each do |assoc|
      if value.class.base_class.to_s.underscore == assoc.to_s
        send( "#{assoc}=", value )
        return
      end
    end
    raise ArgumentError, "Cannot set #{name} to #{value}, no association matches"
  end
  
  # For use in migrations
  define_singleton_method( "update_sql_#{name}_check" ) do |migration|
    constraint = "exactly_one_unpolymorphic_#{name}"
    migration.execute( "ALTER TABLE #{table_name} DROP CONSTRAINT IF EXISTS #{constraint}" )
    migration.execute( "ALTER TABLE #{table_name} ADD CONSTRAINT #{constraint} CHECK (#{associations.collect { |a| "(#{a}_id IS NOT NULL)::int" }.join( " + ")} = 1)" )
  end

  define_singleton_method( "possible_#{name}?" ) do |object|
    return associations.any? { |assoc| object.class.base_class.to_s.underscore == assoc.to_s }
  end
end