controller/views/intsance varialbes

example_controler.rb

# Bad:
class OrdersController
    
    exposes :orders
    
    def index
        @orders = Order.complete
    end
    
    def pending
        @orders = Order.pending
    end
    
end

# Good:
class OrdersController
    
    exposes :complete_orders, :pending_orders
    
    def index
        @complete_orders = Order.complete
    end
    
    def pending
        @pending_orders = Order.pending
    end
    
end

Is this rails 4 or 3?

What's the difference? In official guides they use the bad way.