'get_user_list' function not working

i want to show fullname by using fuction call 'get_user_list' , but
its not working..??

tis s user.rb

(
def full_name
                self.first_name + " " + self.last_name
        end )

my post controller

( def get_user_list
   return User.find(:all, :order => 'last_name ASC').collect {|user|
[user.full_name, user.id]}

NameError in PostsController#edit
undefined local variable or method `get_user_list' for
#<PostsController:0x47c8360>