Unknown parameter in Rails 5.1 strong parameters issue - ruby-on-rails

Question

So my reconciliation model looks like this:
class Reconciliation < ApplicationRecord
belongs_to :location
belongs_to :company
has_and_belongs_to_many :inventory_items
accepts_nested_attributes_for :inventory_items, allow_destroy: true
end
My InventoryItem model looks like this:
class InventoryItem < ApplicationRecord
belongs_to :product
belongs_to :location, inverse_of: :inventory_items
has_and_belongs_to_many :reconciliations
end
In my ReconciliationsController, this is what my reconciliation_params looks like:
def new
#location = Location.find(params[:location_id])
#reconciliation = #location.reconciliations.new
#inventory_items = #location.inventory_items
#start_index = 0
#next_index = #start_index + 1
end
def reconciliation_params
params.require(:reconciliation).permit(:inventory_item_id, :location_id, :display_id, :inventory_items,
inventory_items_attributes: [:id, :quantity_left, :quantity_delivered, :_destroy]
)
end
This is the relevant section of my routes.rb:
resources :locations, shallow: true do
resources :inventory_items
resources :reconciliations
end
This is my views/reconciliations/_form.html.erb:
<%= simple_form_for #reconciliation, url: :location_reconciliations do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :location_id, as: :hidden %>
<%= f.simple_fields_for :inventory_item do |inventory| %>
<%= inventory.input :quantity_left %>
<%= inventory.input :quantity_delivered %>
<% end %>
</div>
<div class="form-actions">
<%= f.button :submit, "Update", class: "btn btn-primary" %>
</div>
<% end %>
This is my app/views/reconciliations/new.html.erb:
<% if params[:next].nil? %>
<%= render 'form', reconciliation: #reconciliation, inventory_item: #inventory_items[#start_index] %>
<% else %>
<%= render 'form', reconciliation: #reconciliation, inventory_item: #inventory_items[#next_index] %>
<% end %>
This is my log when I try to create a reconciliation object:
Started POST "/locations/2/reconciliations" for 127.0.0.1 at 2018-03-24 23:16:33 -0500
Processing by ReconciliationsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"JZvhwloo0+XM9bmptxXGfnDw==", "reconciliation"=>{"location_id"=>"2", "inventory_item"=>{"quantity_left"=>"1", "quantity_delivered"=>"170"}}, "commit"=>"Update", "location_id"=>"2"}
Unpermitted parameter: :inventory_item
Location Load (0.9ms) SELECT "locations".* FROM "locations" WHERE "locations"."id" = $1 LIMIT $2 [["id", 2], ["LIMIT", 1]]
(0.6ms) BEGIN
(0.7ms) ROLLBACK
Rendering reconciliations/new.html.erb within layouts/application
InventoryItem Load (1.0ms) SELECT "inventory_items".* FROM "inventory_items" WHERE "inventory_items"."location_id" = $1 [["location_id", 2]]
Product Load (1.0ms) SELECT "products".* FROM "products" WHERE "products"."id" = $1 LIMIT $2 [["id", 2], ["LIMIT", 1]]
Rendered reconciliations/_form.html.erb (45.9ms)
Rendered reconciliations/new.html.erb within layouts/application (66.8ms)
Rendered shared/_navbar.html.erb (1.3ms)
Completed 200 OK in 202ms (Views: 115.1ms | ActiveRecord: 29.1ms)
I have tried simply adding :inventory_item to my params.require(:reconciliation).permit(..), but that doesn't work.
What am I missing?
Edit 1
When I checked the HTML for the inputs on my form, within the simple_fields_for, the HTML seems to be fine:
<input class="string required" type="text" name="reconciliation[inventory_item][quantity_left]" id="reconciliation_inventory_item_quantity_left">
Edit 2
When I change the simple_fields_for call to be plural, i.e. :inventory_items, rather than :inventory_item like this:
That entire portion of the form disappears altogether.
This is what the HTML looks like:
<div class="form-inputs">
<div class="input hidden reconciliation_location_id"><input class="hidden" type="hidden" value="2" name="reconciliation[location_id]" id="reconciliation_location_id"></div>
</div>
This is how the HTML looks when that simple_field_for :inventory_item is singular:
<div class="form-inputs">
<div class="input hidden reconciliation_location_id"><input class="hidden" type="hidden" value="2" name="reconciliation[location_id]" id="reconciliation_location_id"></div>
<div class="input string required reconciliation_inventory_item_quantity_left"><label class="string required" for="reconciliation_inventory_item_quantity_left"><abbr title="required">*</abbr> Quantity left</label><input class="string required" type="text" name="reconciliation[inventory_item][quantity_left]" id="reconciliation_inventory_item_quantity_left"></div>
<div class="input string required reconciliation_inventory_item_quantity_delivered"><label class="string required" for="reconciliation_inventory_item_quantity_delivered"><abbr title="required">*</abbr> Quantity delivered</label><input class="string required" type="text" name="reconciliation[inventory_item][quantity_delivered]" id="reconciliation_inventory_item_quantity_delivered"></div>
</div>

Answer 1

I have tried simply adding :inventory_item to my params.require(:reconciliation).permit(..), but that doesn't work.
If you want permit inventory_item, you must specify its structure, because it is not a simple field, but a hash:
def reconciliation_params
params.require(:reconciliation).permit(:location_id, :display_id, inventory_item: [:id, :quantity_left, :quantity_delivered] )
end
By looking at your log, you are not passing the inventory_item_id, which might be needed to update this specific item:
Parameters: {"utf8"=>"✓", "authenticity_token"=>"JZvhwloo0+XM9bmptxXGfnDw==",
"reconciliation"=>{"location_id"=>"2", "inventory_item"=>
{"quantity_left"=>"1", "quantity_delivered"=>"170"}},
"commit"=>"Update", "location_id"=>"2"}
You could add it as a hidden field in the nested form.

Answer 2

Form of association should be plural f.simple_fields_for :inventory_items.
You should initialize a new inventory_item object in the new controller's action
def new
#reconciliation = Reconciliation.new
# you can create as many new items as you want
#reconciliation.inventory_items.build
end
If you want to dynamically add items to the form i advise you to use https://github.com/nathanvda/cocoon
BUT it looks like you want to add existing inventory_item to a new reconciliation, you better use has_many through assocations http://guides.rubyonrails.org/association_basics.html#choosing-between-has-many-through-and-has-and-belongs-to-many
Its easier to add a join model objects with neccessary fields and associations.
Another advise: do not send local variable to partial if you are using instance variable in this partial
# render partial
render 'form', reconciliation: #reconciliation
# partial with form for local variable
simple_form_for reconciliation
and i think your form partial will not work for the edit action because of hardcoded url, you can pass url in a variable:
# new html
render 'form', reconciliation: #reconciliation, url_var: location_reconciliations(#location)
# edit
render 'form', reconciliation: #reconciliation, url_var: reconciliations(#reconciliation)
# form
simple_form_for reconciliation, url: url_var