Nested_attributes in Form Helper - what is the "Rails way"?

We are working with nested attributes and we’ve reached a point where
we’re
not sure if there is a better, clearer, “more rails” way of dealing with
it.

We have 3 models - Organisation, Category and a strictly join table
CategoryOrganisation (no additional attributes). The relation between
Organisation and Category is many-to-many.

Now, we want to create a form with checkboxes through which the
categories
for organisations can be added and removed. The example form would look
like that:

[image: form1]
https://cloud.githubusercontent.com/assets/12682792/14636248/993263cc-062a-11e6-85a2-de8388a75a3f.PNG

Now, the form should behave like that:

  • when new action is hit, it should show all categories - unchecked,
  • when create action is hit, but validations are not passing it
    should
    render the new view, but keeping the checkboxes that were selected,
  • when edit action is hit, is should show all categories and current
    categories of the edited organisation should be checked,
  • when create and update are successful, flow is redirected to show
    action.

We don’t want to spoil your minds with our custom solution, but to get
to
know if there is a clear, Rails solution for that.

In our opinion, there is no such solution in Rails documentation, as we
found out reading following sources:

http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html,

http://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html
.

API documentation doesn’t get to many-to-many relation, which is the
case
in our app.

In advance, thanks for help!

Have you looked at
http://apidock.com/rails/v4.0.2/ActionView/Helpers/FormOptionsHelper/collection_check_boxes
? Seems to be exactly what you want.

On Tuesday, April 19, 2016 at 4:09:21 PM UTC+1, Piotr Brych wrote:

for organisations can be added and removed. The example form would look
like that:

As long as you don’t want the same form to be usable to create new
categories, I wouldn’t use nested attributes at all.

f.collection_check_boxes :category_ids, Category.all, :id, :name

will render a checkbox and label for each category, and the check box
will
be ticked if category_ids contains the element (there are plenty of
options
to customise the generated markup). I’m not entirely sure what happens
if
you assign to foo_ids but the overall save fails and rolls back. If you
run
into issues there I’d add a virtual attribute to hold the assigned ids
and
actually set category_ids from a before_save or similar.

Fred

OK, thanks for that, it might help.

But how would you in this case send params back to create or update
to
respectively know which associations (category_organisations) should be
created and which deleted?

Thanks,
Piotr

W dniu wtorek, 19 kwietnia 2016 17:19:21 UTC+2 użytkownik Frederick
Cheung
napisał:

On Wednesday, April 20, 2016 at 2:26:20 PM UTC+1, Piotr Brych wrote:

OK, thanks for that, it might help.

But how would you in this case send params back to create or update to
respectively know which associations (category_organisations) should be created
and which deleted?

Assigning to category_ids will create/delete rows in the join table as
appropriate.

Fred.

Piotr, have a look at

There are a ton of things that are auto-created by associations - one is
a
setter method that reflects the id’s of the association.
#collection_check_boxes basically formats your input to match that
setter.
In this case it would be “category_ids”.

On Wed, Apr 20, 2016 at 1:54 PM, Frederick C. <

Thank you guys, you helped us a lot! Great to have you around :).

Piotr

W dniu środa, 20 kwietnia 2016 20:04:59 UTC+2 użytkownik Stewart
Mckinney
napisał:

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs