instance method `cattr_reader`

Ruby on Rails 4.0.13

Since v2.2.3 Last seen in v4.0.13

Available in: v2.2.3 v2.3.18 v3.0.20 v3.1.12 v3.2.22.5 v4.0.13

Compare with:

cattr_reader(*syms)

Defines a class attribute if it’s not defined and creates a reader method that returns the attribute value.

class Person
  cattr_reader :hair_colors
end

Person.class_variable_set("@@hair_colors", [:brown, :black])
Person.hair_colors     # => [:brown, :black]
Person.new.hair_colors # => [:brown, :black]

The attribute name must be a valid method name in Ruby.

class Person
  cattr_reader :"1_Badname "
end
# => NameError: invalid attribute name

If you want to opt out the instance reader method, you can pass instance_reader: false or instance_accessor: false.

class Person
  cattr_reader :hair_colors, instance_reader: false
end

Person.new.hair_colors # => NoMethodError

Parameters

syms rest

Source

# File activesupport/lib/active_support/core_ext/class/attribute_accessors.rb, line 32
  def cattr_reader(*syms)
    options = syms.extract_options!
    syms.each do |sym|
      raise NameError.new("invalid class attribute name: #{sym}") unless sym =~ /^[_A-Za-z]\w*$/
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        unless defined? @@#{sym}
          @@#{sym} = nil
        end

        def self.#{sym}
          @@#{sym}
        end
      EOS

      unless options[:instance_reader] == false || options[:instance_accessor] == false
        class_eval(<<-EOS, __FILE__, __LINE__ + 1)
          def #{sym}
            @@#{sym}
          end
        EOS
      end
    end
  end

Defined in activesupport/lib/active_support/core_ext/class/attribute_accessors.rb line 32 · View on GitHub · Improve this page · Find usages on GitHub

Defined in Class

Signature

Parameters