Nested form in active_admin with select or create option - ruby-on-rails

Question

We are using active_admin for our administration backend.
We have a model "App" that :belongs_to model "Publisher":
class App < ActiveRecord::Base
belongs_to :publisher
end
class Publisher < ActiveRecord::Base
has_many :apps
end
When creating a new entry for the "App" model I want to have the option to either select an existing publisher or (if the publisher is not yet created) to create a new publisher in the same (nested) form (or at least without leaving the page).
Is there a way to do this in active_admin?
Here's what we have so far (in admin/app.rb):
form :html => { :enctype => "multipart/form-data" } do |f|
f.inputs do
f.input :title
...
end
f.inputs do
f.semantic_fields_for :publisher do |p| # this is for has_many assocs, right?
p.input :name
end
end
f.buttons
end
After hours of searching, I'd appreciate any hint... Thanks!

Answer 1

First, make sure that in your Publisher model you have the right permissions for the associated object:
class App < ActiveRecord::Base
attr_accessible :publisher_attributes
belongs_to :publisher
accepts_nested_attributes_for :publisher, reject_if: :all_blank
end
Then in your ActiveAdmin file:
form do |f|
f.inputs do
f.input :title
# ...
end
f.inputs do
# Output the collection to select from the existing publishers
f.input :publisher # It's that simple :)
# Then the form to create a new one
f.object.publisher.build # Needed to create the new instance
f.semantic_fields_for :publisher do |p|
p.input :name
end
end
f.buttons
end
I'm using a slightly different setup in my app (a has_and_belongs_to_many relationship instead), but I managed to get it working for me. Let me know if this code outputs any errors.

Answer 2

The form_builder class supports a method called has_many.
f.inputs do
f.has_many :publisher do |p|
p.input :name
end
end
That should do the job.
Update: I re-read your question and this only allows to add a new publisher, I am not sure how to have a select or create though.

Answer 3

According to ActiveAdmin: http://activeadmin.info/docs/5-forms.html
You just need to do as below:
f.input :publisher

Answer 4

I've found you need to do 3 things.
Add semantic fields for the form
f.semantic_fields_for :publisher do |j|
j.input :name
end
Add a nested_belongs_to statement to the controller
controller do
nested_belongs_to :publisher, optional: true
end
Update your permitted parameters on the controller to accept the parameters, using the keyword attributes
permit_params publisher_attributes:[:id, :name]