mattr_accessor(*syms, &blk)
Instance Public methods
Defines both class and instance accessors for class attributes.
module HairColors mattr_accessor :hair_colors end class Person include HairColors end Person.hair_colors = [:brown, :black, :blonde, :red] Person.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 Male < Person end Male.hair_colors << :blue Person.hair_colors # => [:brown, :black, :blonde, :red, :blue]
To opt out of the instance writer method, pass instance_writer:
false
. To opt out of 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 opt out 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
Also you can pass a block to set up the attribute with a default value.
module HairColors mattr_accessor :hair_colors do [:brown, :black, :blonde, :red] end end class Person include HairColors end Person.class_variable_get("@@hair_colors") #=> [:brown, :black, :blonde, :red]
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