如何“继承” ApplicationController中的类变量

Question

I'm a little new to rails.

Say I want to do something like:

def is_admin?
 @admin = User.grab(session[:username]).admin
end

I can define this in the ApplicationController but then I have to call is_admin?() in every method in every subsequent controller. Is there a way around this that I am not aware of?

Answer 1

Use a :before_filter at the start of each controller:

before_filter :is_admin

At least then you don't have to do it for every method.

Answer 2

I'm not sure exactly what the problem with calling is_admin? is. Calling methods in Ruby is pretty cheap. You may want to "memoize" the return value to avoid calling to the database every time the method is called:

def is_admin?
  unless defined?(@is_admin)
    @is_admin = User.grab(session[:username]).admin
  end

  @is_admin
end

Since is_admin? can return a falsey value, ||= won't work.