method

define_attr_method

v3.0.9 - Show latest stable - 0 notes - Class: ActiveModel::AttributeMethods::ClassMethods

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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 95
      def define_attr_method(name, value=nil, &block)
        sing = singleton_class
        sing.class_eval           if method_defined?(:'original_#{name}')            undef :'original_#{name}'          end          alias_method :'original_#{name}', :'#{name}', __FILE__, __LINE__ + 1
        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               def #{name}; #{value.nil? ? 'nil' : value.to_s.inspect}; end, __FILE__, __LINE__ + 1
          else
            value = value.to_s if value
            sing.send(:define_method, name) { value }
          end
        end
      end

define_attr_method

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