method

define_attr_method

v3.0.0 - Show latest stable - 0 notes - Class: ActiveModel::AttributeMethods::ClassMethods

1.0.0
1.1.6
1.2.6
2.0.3
2.1.0
2.2.1
2.3.8
3.0.0 (0)
3.0.9 (-2)
3.1.0 (0)
3.2.1 (-38)
3.2.8 (0)
3.2.13 (0)
4.0.2
4.1.8
4.2.1
4.2.7
4.2.9
5.0.0.1
5.1.7
5.2.3
6.0.0
6.1.3.1
6.1.7.7
7.0.0
7.1.3.2
7.1.3.4
What's this?

define_attr_method(name, value=nil, &block) public

Defines an "attribute" method (like inheritance_column or table_name). A new (class) method will be created with the given name. If a value is specified, the new method will return that value (as a string). Otherwise, the given block will be used to compute the value of the method.

The original method will be aliased, with the new name being prefixed with "original_". This allows the new method to access the original value.

Example:

  class Person

    include ActiveModel::AttributeMethods

    cattr_accessor :primary_key
    cattr_accessor :inheritance_column

    define_attr_method :primary_key, "sysid"
    define_attr_method( :inheritance_column ) do
      original_inheritance_column + "_id"
    end

  end

Provides you with:

  AttributePerson.primary_key
  # => "sysid"
  AttributePerson.inheritance_column = 'address'
  AttributePerson.inheritance_column
  # => 'address_id'

Show source

# File activemodel/lib/active_model/attribute_methods.rb, line 93
      def define_attr_method(name, value=nil, &block)
        sing = singleton_class
        sing.class_eval "if method_defined?(:original_\#{name})\nundef :original_\#{name}\nend\nalias_method :original_\#{name}, :\#{name}\n", __FILE__, __LINE__ + 1
        if block_given?
          sing.send :define_method, name, &block
        else
          # use eval instead of a block to work around a memory leak in dev
          # mode in fcgi
          sing.class_eval "def \#{name}; \#{value.to_s.inspect}; end\n", __FILE__, __LINE__ + 1
        end
      end

define_attr_method

Related methods