instance method
mattr_accessor
Ruby on Rails edge
Signature
mattr_accessor(*syms, instance_reader: true, instance_writer: true, instance_accessor: true, default: nil, &blk)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] “‘
Parameters
-
symsrest -
instance_readerkey = true -
instance_writerkey = true -
instance_accessorkey = true -
defaultkey = nil -
blkblock
Source
# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 241
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
Defined in activesupport/lib/active_support/core_ext/module/attribute_accessors.rb line 241
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