Can't use methods in the application helper for cancan ability.rb

Question

I'm using Devise and cancancan. In my application helper I have -

def is_part_of_team?(book)
    on_team = false
    book.contributions.each do |contribution|
        if contribution.user == current_user
            on_team = true
        end
    end
    if book.user == current_user
        on_team = true
    end
    return on_team
end

and in ability.rb I have -

include ApplicationHelper
...
can :update, Book do |book|
  is_part_of_team?(book)
end

... this throws the error -

undefined local variable or method `current_user' for #<Ability...

There are probably better ways of doing this, but I just wondered why cancan does not like current_user within the application helper. Why is this? I use this function from views and it's all dandy.

Answer 1

My approach was bad altogether.

Instead of all that code in the helper, I hadn't understood that I could use this -

book.contributions.where(user_id: user.id).any?

...to get exactly the same result. This means in ability.rb I can have this -

  can :update, Book do |book|
    (book.try(:user) == user) || book.contributions.where(user_id: user.id).any?
  end