Rails extends Ruby with both mattr_accessor
(Module accessor) and cattr_accessor
(as well as _reader
/_writer
versions). As Ruby’s attr_accessor
generates getter/setter methods for instances, cattr/mattr_accessor
provide getter/setter methods at the class or module level. Thus:
module Config
mattr_accessor :hostname
mattr_accessor :admin_email
end
is short for:
module Config
def self.hostname
@hostname
end
def self.hostname=(hostname)
@hostname = hostname
end
def self.admin_email
@admin_email
end
def self.admin_email=(admin_email)
@admin_email = admin_email
end
end
Both versions allow you to access the module-level variables like so:
>> Config.hostname = "example.com"
>> Config.admin_email = "admin@example.com"
>> Config.hostname # => "example.com"
>> Config.admin_email # => "admin@example.com"