Variable scope in rails controller


I would like to know variable scope for variable accessibility in all
rails controller methods.

for example, I had done like below.

class app_controller

def set_vaule
@var = "12gfjdl"

def actions1
  need display @var here

def action2
here also need @var value


note: I had tried with session and declare @var as class variable(@@var)
it access only first time, later if I made any request again the action
is set to nil i.e
uninitialised class variable.

An instance variable (@...) is available in any method. Note though
that since the controller is reconstructed for each request it will
not survive between requests (so in the above you might want a
before_filter calling set_value). To have a persistent object that
survives over multiple requests (per user) then use the session.

If something is always a fixed value then use a constant.