Objects in Views

Rails
1

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.

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 S…

Stephen
Leacockhttp://www.brainyquote.com/quotes/authors/s/stephen_leacock.html

  • “I detest life-insurance agents: they always argue that I shall some
    day
    die, which is not so.”
2

2009/8/29 Dhruva S. [email protected]:

@model2 = Model2.all
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’ IÂ 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

3

On Sat, Aug 29, 2009 at 1:21 PM, Colin L. [email protected]
wrote:

@model2 being nil. I don’t understand the reason for the same, I am
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.

Thanks & Regards,
Dhruva S…

Pablo
Picassohttp://www.brainyquote.com/quotes/authors/p/pablo_picasso.html

  • “Computers are useless. They can only give you answers.”
4

2009/8/29 Dhruva S. [email protected]:

in

But in the event some of my validations fail and in the controller I do
sent to the browser, then they are discarded. Â Therefore when you get

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

5

That’s interesting, again thank you very much for you help.
I too think that your idea is better :slight_smile:

Thanks & Regards,
Dhruva S…

Samuel
Goldwynhttp://www.brainyquote.com/quotes/authors/s/samuel_goldwyn.html

  • “I’m willing to admit that I may not always be right, but I am never
    wrong.”