Refactor code to avoid circular logic in controller - ruby-on-rails

Question

Situation:
One form that allows users to select multiple quantities of items they'd like to request
This form POSTs to two models, one parent: Request, and child: Items.
Upon submit, one Request is created, but up to several Items are created, depending on the quantity indicated
To handle this, I have two sets of params, one for the Items, one for Requests
Desired end state:
I do not want an Item to be created without a Request nor a Request to be created without the Item
All the errors present in the form (whether it's not selecting at least one item, or errors in the attributes of the Request object) are shown together to the user once the page is re-rendered; i.e., I would like to do all the error checking together
Current hacky solution & complication:
Currently, I'm checking in stages, 1) are there quantities in the Items? If not, then regardless of what the user may have put for Request attributes, the page is re-rendered (i.e., all attributes for Request are lost, as are any validation errors that would be shown). 2) Once the first stage is passed, then the model validations kicks in, and if it fails, the new page is re-rendered again
I've spent waaaaay too long thinking about this, and nothing elegant comes to mind. Happy with the hacky solution, but would love insights from much smarter people!
Controller code (fat for now, will fix later)
def create
request_params
#requestrecord = #signup_parent.requests.build
if #itemparams.blank?
#requestrecord.errors[:base] = "Please select at least one item"
render 'new'
else
#requestrecord = #signup_parent.requests.create(#requestparams)
if #requestrecord.save
items_to_be_saved = []
#itemparams.each do |item, quantity|
quantity = quantity.to_i
quantity.times do
items_to_be_saved << ({:request_id => 0, :name => item })
end
end
Item.create items_to_be_saved
flash[:success] = "Thanks!"
redirect_to action: 'success'
else
render 'new'
end
end
end
def request_params
#requestparams = params.require(:request).permit(:detail, :startdate, :enddate)
#itemparams = params["item"]
#itemparams = #transactionparams.first.reject { |k, v| (v == "0") || (v == "")}
end
And in case it's helpful, the snippet of the view code that generates the params["item"]
<% itemlist.each do |thing| %>
<%= number_field_tag "item[][#{thing}]", :quantity, min: 0, placeholder: 0 %>
<%= label_tag thing %>
</br>
<% end %>
<!-- itemlist is a variable in the controller that is populated with a list of items -->

Answer 1

Validations
When you mention you want all the errors to be returned at the same time, it basically means you need to use the Rails' validations functionality.
This populates the #model.errors object, which you can then use on your form like this:
<% if #model.errors.any? %>
<ul>
<% #model.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
I think your problem is you're trying to use the validations in the controller. This is both against MVC principles & generally bad for programming modularity. The functionality you require is available with the validations features:
You may benefit from using inverse_of to create some conditional validations; or using reject_if
reject_if
#app/models/request.rb
Class Request < ActiveRecord::Base
accepts_nested_attributes_for :items, reject_if: proc { |attributes| attributes['an_item_param'].blank? #-> attributes are the "item" attributes }
end
This will only be triggered if a request is created. I.E if your request fails for some reason (validation issue), the accepts_nested_attributes_for method will not run, returning your object with the appended errors
This is mainly used to validate the nested resources (I.E you can't save an item unless its title attribute is populated etc)
--
inverse_of
#app/models/request.rb
Class Request < ActiveRecord::Base
has_many :items, inverse_of: :request
accepts_nested_attributes_for :items
end
#app/models/item.rb
Class Item < ActiveRecord::Base
belongs_to :request, inverse_of: :items
validates :title, presence: true, unless: :draft?
private
def draft?
self.request.draft #-> an example we've used before :)
end
end
This is more for model-specific validations; allowing you to determine specific conditions. We use this if we want to save a draft etc