mattr_reader(*syms)
Instance Public methods
Defines a class attribute and creates a class and instance reader methods.
The underlying the class variable is set to nil, if it is not
previously defined.
module HairColors
mattr_reader :hair_colors
end
HairColors.hair_colors # => nil
HairColors.class_variable_set("@@hair_colors", [:brown, :black])
HairColors.hair_colors # => [:brown, :black]
The attribute name must be a valid method name in Ruby.
module Foo mattr_reader :"1_Badname " end # => NameError: invalid attribute name
If you want to opt out the creation on the instance reader method, pass
instance_reader: false or instance_accessor:
false.
module HairColors mattr_writer :hair_colors, instance_reader: false end class Person include HairColors end Person.new.hair_colors # => NoMethodError
Also, you can pass a block to set up the attribute with a default value.
module HairColors
cattr_reader :hair_colors do
[:brown, :black, :blonde, :red]
end
end
class Person
include HairColors
end
Person.hair_colors # => [:brown, :black, :blonde, :red]
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