method

cattr_writer

Ruby on Rails latest stable (v6.1.7.7) - 1 note - Class: Class

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What's this?

Method deprecated or moved

This method is deprecated or moved on the latest stable version. The last existing version (v4.0.2) is shown here.

These similar methods exist in v6.1.7.7:

Module#cattr_writer

cattr_writer(*syms) public

Defines a class attribute if it’s not defined and creates a writer method to allow assignment to the attribute.

class Person
  cattr_writer :hair_colors
end

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

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

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

If you want to opt out the instance writer method, pass instance_writer: false or instance_accessor: false.

class Person
  cattr_writer :hair_colors, instance_writer: false
end

Person.new.hair_colors = [:blonde, :red] # => NoMethodError

Also, you can pass a block to set up the attribute with a default value.

class Person
  cattr_writer :hair_colors do
    [:brown, :black, :blonde, :red]
  end
end

Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]

Show source

# File activesupport/lib/active_support/core_ext/class/attribute_accessors.rb, line 93
  def cattr_writer(*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(        unless defined? @@#{sym}          @@#{sym} = nil        end        def self.#{sym}=(obj)          @@#{sym} = obj        end, __FILE__, __LINE__ + 1)

      unless options[:instance_writer] == false || options[:instance_accessor] == false
        class_eval(          def #{sym}=(obj)            @@#{sym} = obj          end, __FILE__, __LINE__ + 1)
      end
      send("#{sym}=", yield) if block_given?
    end
  end

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

1 thank

Description

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

cattr_writer

Related methods

Method deprecated or moved

Description

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