define_attr_method(name, value=nil, &block) — ActiveModel::AttributeMethods::ClassMethods

define_attr_method(name, value=nil, &block)

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:

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

Parameters

name req
value opt = nil
block block

Source

# File activemodel/lib/active_model/attribute_methods.rb, line 100
      def define_attr_method(name, value=nil, &block)
        sing = singleton_class
        sing.class_eval <<-eorb, __FILE__, __LINE__ + 1
          if method_defined?('original_#{name}')
            undef :'original_#{name}'
          end
          alias_method :'original_#{name}', :'#{name}'
        eorb
        if block_given?
          sing.send :define_method, name, &block
        else
          # If we can compile the method name, do it. Otherwise use define_method.
          # This is an important *optimization*, please don't change it. define_method
          # has slower dispatch and consumes more memory.
          if name =~ COMPILABLE_REGEXP
            sing.class_eval <<-RUBY, __FILE__, __LINE__ + 1
              def #{name}; #{value.nil? ? 'nil' : value.to_s.inspect}; end
            RUBY
          else
            value = value.to_s if value
            sing.send(:define_method, name) { value }
          end
        end
      end

Defined in activemodel/lib/active_model/attribute_methods.rb line 100 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveModel::AttributeMethods::ClassMethods

Signature

Parameters