Rails params for nested forms - ruby-on-rails

Question

I've been battling for days now to get data to save for my nested form. I basically want to be able to store a users reason for cancelling a project, along with the last stage of the project before it was cancelled. But I just can't seem to get the actions cancel, cancel_save, and cancel_params to play nicely!
Controller
before_action :correct_user, only: [:show, :edit, :update, :destroy, :cancel, :cancel_save]
...
def cancel
#project.build_project_close_reason
end
def cancel_save
#project.build_project_close_reason(cancel_params)
#project.update(project_status_id: 10)
redirect_to root_path, notice: 'Project has been successfully cancelled.'
end
private
def correct_user
#user = current_user
#project = current_user.projects.find_by(id: params[:id])
end
redirect_to user_projects_path, notice: "You are not authorised to view this project" if #project.nil?
end
def cancel_params
params.require(:project).permit(project_close_reason_attributes: [:comment]).merge(project_close_reason_attributes: [project_id: #project.id, last_status_id: #project.project_status_id ])
end
Models
class Project < ApplicationRecord
belongs_to :user
has_one :project_close_reason
accepts_nested_attributes_for :project_close_reason #adding this seemed to make no difference?
end
class ProjectCloseReason < ApplicationRecord
belongs_to :project
end
class User < ApplicationRecord
... # All standard devise stuff
has_many :projects
end
Nested form in the view
<%= form_for([#user, #project], url: {action: "cancel_save"}, method: :post) do |f| %>
<%= fields_for :project_close_reason do |pcr| %>
<div class="field entry_box">
<%= pcr.label "Why are you cancelling this project? (This helps us improve!)" %>
<%= pcr.text_area :comment, class: "form-control entry_field_text" %>
</div>
<% end %>
<div class="actions center space_big">
<%= f.submit "Cancel Project", class: "btn btn-lg btn-warning" %>
</div>
<% end %>
Routes
devise_for :users
devise_for :admins
resources :users do
resources :projects do
get "cancel", :on => :member
post "cancel" => 'projects#cancel_save', :on => :member
end
end
This is the error I get when I try and submit the form:
ActionController::ParameterMissing in ProjectsController#cancel_save
param is missing or the value is empty: project. It references the cancel_params action
Thanks for any help!
UPDATE
Here is the log when I call cancel_save
Started POST "/users/2/projects/10/cancel" for ::1 at 2016-09-29 10:03:44 +0200
Processing by ProjectsController#cancel_save as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"h6K+VFyjW/dV189YOePWZm+Pmjey50xAMQIJb+c3dzpEaMv8Ckh3jQGOWfVdlfVH/FxolbB45fXvTO0cdplhkg==", "project_close_reason"=>{"comment"=>"b"}, "commit"=>"Cancel Project", "user_id"=>"2", "id"=>"10"}
User Load (11.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2 [["id", 2], ["LIMIT", 1]]
Project Load (0.7ms) SELECT "projects".* FROM "projects" WHERE "projects"."user_id" = $1 AND "projects"."id" = $2 LIMIT $3 [["user_id", 2], ["id", 10], ["LIMIT", 1]]
ProjectCloseReason Load (0.2ms) SELECT "project_close_reasons".* FROM "project_close_reasons" WHERE "project_close_reasons"."project_id" = $1 LIMIT $2 [["project_id", 10], ["LIMIT", 1]]
Completed 400 Bad Request in 22ms (ActiveRecord: 12.1ms)
ActionController::ParameterMissing (param is missing or the value is empty: project):

Answer 1

The error is saying that there is no params with name project, which you are trying to require in params.require(:project) line in cancel params. I think this is happening beacause in form_for you have mentioned [#user, #project], that means user's project. So the project params must be inside user's. Check your log when you call cancel_save. There must be something like {user => {project => { } }.

Answer 2

In the end I got it to work without requiring projects at all. This is my revised cancel_params in my projects_controller. For anyone else looking at doing this kind of additive databasing, I highly recommend skipping params for nested form if you can do it this way. So much simpler!
private
def cancel_params
params.require(:project_close_reason).permit(:comment).merge(project_id: #project.id, last_status_id: #project.project_status_id )
end