We all know Active Support library constantly keeps adding new extensions to ruby core library and hence rails framework.
Do you know now inside ruby class we can have class_attribute placeholder.
class A
class_attribute :counter, :access_time
end
A.counter = 12
A.counter #=> 12
A.new.counter #=> 12
Inheritance
class B < A
end
B.counter #=> 12
B.access_time #=> nil
B.access_time = Time.now
B.access_time #=> Wed Dec 28 18:55:06 +0530 2011
B.new.access_time #=> Wed Dec 28 18:55:06 +0530 2011
A.access_time = nil
Restricting instance from writing class_attributes
class V
class_attribute :counter, :instance_writer => false
end
V.new.counter = 12
NoMethodError: undefined method `counter=' for #
Other ways
a_class = Class.new{class_atrribute :counter}
a_class.counter = 13
a_class.counter #=> 13
a_class.new.counter #=> 13
p = Class.new { class_attribute :help, :instance_writer => false }
p.new.help = 'Got a second!'
NoMethodError: undefined method `help=' for #<#:0x7f8f9d5b1038>
p.help = 'Got a second!'
p.help #=> "Got a second!"
