Re: [Rails] one_to_many relationship, auto update?

On 27 November 2011 21:27, kahou l. <lists@ruby-forum.com> wrote:
> Hi,
>
> I am new to Ruby on Rail. I have a question regarding the one_to_many
> relationship which doesn't automatically update the relationship by
> Rails.
>
> Support I have two classes: Car and Wheel.
>
> Car has many Wheel where as Wheel belongs to Car. Therefore, I declare
> the classes as below:
>
> // car.rb
> class Car < ActiveRecord::Base
>        has_many :wheels
> end
>
> // wheel.rb
> class Wheel < ActiveRecord::Base
>        belongs_to :car
> end
>
> The is how I test drive in rails console:
>
> car1 = Car.new
> car1.save
>
> car2 = Car.new
> car2.save
>
> wheel1 = Wheel.new
> wheel1.save
>
> wheel2 = Wheel.new
> whee2.save
>
> car1.wheels << wheel1
>
> car1.wheels << wheel2
> car2.wheels << wheel2
>
> Note that car1 wheels STILL contains wheel2 when I reassign wheel2 to
> car2.
> I expect car1 doesn't have wheel2 anymore...
>
> I don't know why it doesn't get update automatically that car1 shouldn't
> contains wheel2 anymore. Can anybody help me to solve this problem?

Try fetching car1 from the database again, I suspect it is just that
the version in memory does not know that you have removed one of its
wheels. I think there is a way of asking it to refresh itself to save
explicitly fetching it, but I cannot bring it to mind at the moment.

Colin

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