method

cattr_reader

Ruby on Rails latest stable (v3.2.13) - 2 notes - Class: Class

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What's this?

cattr_reader(*syms) public

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

Show 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|
      class_eval(        unless defined? @@#{sym}          @@#{sym} = nil        end        def self.#{sym}          @@#{sym}        end, __FILE__, __LINE__ + 1)

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

January 27, 2009 - (v2.1.0 - v2.2.1)

2 thanks

Description

Similar to Ruby’s built-in attr_reader, only it creates a class attribute reader method (as opposed to an instance attribute reader method).

February 2, 2013

0 thanks

Other Example

class Exam
 cattr_reader :code, :description, :points, :instance_reader => false

 @@code = "EXM"
 @@description = "Sent Exam"
 @@points = 1000
end

In this case it’s possible to use

Exam.code # => EXM
Exam.description # => Sent Exam
Exam.points # => 1000

cattr_reader

Related methods

Description

Other Example

In this case it’s possible to use

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