Method: Module#cattr_accessor
- Defined in:
- activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
#cattr_accessor ⇒ Object
Defines both class and instance accessors for class attributes. All class and instance methods created will be public, even if this method is called with a private or protected access modifier.
module HairColors
mattr_accessor :hair_colors
end
class Person
include HairColors
end
HairColors.hair_colors = [:brown, :black, :blonde, :red]
HairColors.hair_colors # => [:brown, :black, :blonde, :red]
Person.new.hair_colors # => [:brown, :black, :blonde, :red]
If a subclass changes the value then that would also change the value for parent class. Similarly if parent class changes the value then that would change the value of subclasses too.
class Citizen < Person
end
Citizen.new.hair_colors << :blue
Person.new.hair_colors # => [:brown, :black, :blonde, :red, :blue]
To omit the instance writer method, pass instance_writer: false
. To omit the instance reader method, pass instance_reader: false
.
module HairColors
mattr_accessor :hair_colors, instance_writer: false, instance_reader: false
end
class Person
include HairColors
end
Person.new.hair_colors = [:brown] # => NoMethodError
Person.new.hair_colors # => NoMethodError
Or pass instance_accessor: false
, to omit both instance methods.
module HairColors
mattr_accessor :hair_colors, instance_accessor: false
end
class Person
include HairColors
end
Person.new.hair_colors = [:brown] # => NoMethodError
Person.new.hair_colors # => NoMethodError
You can set a default value for the attribute.
module HairColors
mattr_accessor :hair_colors, default: [:brown, :black, :blonde, :red]
mattr_accessor(:hair_styles) { [:long, :short] }
end
class Person
include HairColors
end
Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
Person.class_variable_get("@@hair_styles") # => [:long, :short]
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# File 'activesupport/lib/active_support/core_ext/module/attribute_accessors.rb', line 213 def mattr_accessor(*syms, instance_reader: true, instance_writer: true, instance_accessor: true, default: nil, &blk) location = caller_locations(1, 1).first mattr_reader(*syms, instance_reader: instance_reader, instance_accessor: instance_accessor, default: default, location: location, &blk) mattr_writer(*syms, instance_writer: instance_writer, instance_accessor: instance_accessor, default: default, location: location) end |