2009/8/29 Dhruva Sagar <[email protected]>:
> On Sat, Aug 29, 2009 at 1:21 PM, Colin Law <[email protected]> wrote:
>>
>> 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
>
> Hi Colin,
>
> Thank you very much for your input, I understand it now & yes it happens
> with edit as well.
> I think helpers is perhaps the best place to put the code for the
> @model.collect in.
>
You could ask yourself who knows what are the valid options that a
user may select? The answer may be the model, depending on your
application. If so then put it in a model method. I am not talking
about how to display the selection (drop down, radio buttons, check
boxes or whatever), that is a decision for the view and it's helpers.
Possibly in the future there may be a need to disallow certain
selections based on criteria in the db. In this case if a model
method provides the selection the change will be in the model. If you
have code like
f.select :model1_id, Model1.all.collect { |m1| [m1.name, m1.id] }
in the view/helper then it becomes messy.
f.select :model1_id, Model1.get_selection_data
is arguably better.
Colin
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