2009/8/29 Dhruva Sagar <[email protected]>:
> Hi everyone,
>
> I have recently experienced a strange behavior (strange from my knowledge)
> in rails.
>
> In my controllers 'new' action, I am creating a few instance variables in
> the following manner :
>
> @controllerModel = ControllerModel.new
> @model1 = Model1.all
> @model2 = Model2.all
>
> in my 'new' view, I am using the @controllerModel to create the form for new
> and I am using the @model1 & @model2 within the form to populate 2 combo
> boxes in the following manner :
>
> f.select :model1_id, @model1.collect { |m1| [m1.name, m1.id] }
>
> f.select :model2_id, @model2.collect { |m2| [m2.name, m2.id] }
>
> Now everything works fine, the form is generated fine, there are no errors
> even the form submit works fine when I ensure that all the required fields
> (ControllerModel validations).
>
> But in the event some of my validations fail and in the controller I do a
> render :action => 'new' I am given an error / exception for @model1 &
> @model2 being nil. I don't understand the reason for the same, I am looking
> for an explanation for this.
>
The reason is that the @model1 and @model2 variables are only
available for the initial render of new. They are setup by you in the
controller, used in the view erb file to generate the html which is
sent to the browser, then they are discarded. Therefore when you get
validation failures and wish to show the view again you must set up
the variables again. One solution is to have a private method of the
controller called something like prepare_for_edit_or_new which you
call where appropriate (you will likely have the same problem in edit)
or, the solution I prefer, is to have Model1 and Model2 methods
get_selection_data or similar that return the equivalent of
@model1.collect { |m1| [m1.name, m1.id] } and then call this directly
from the view, thus eliminating the need for the variables.
Colin
> As a work around of course I found that if I add the following to the view
> it works out fine, but I don't understand the flow fully, I want to know why
> the above mentioned error occurs.
>
> work around in 'new' view :
>
> if @controllerModel.errors
> @model1 = Model1.all
> @model2 = Model2.all
> end
>
> Thanks & Regards,
> Dhruva Sagar.
>
>
> Stephen Leacock - "I detest life-insurance agents: they always argue that I
> shall some day die, which is not so."
> >
>
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