Rails 3.2更新嵌套属性

Question

Here's my problem. If I go to Projects#edit , I am unable to change the course it is assigned to. If I attempt to create a new course for it, or choose from an existing one, I get the following error:

Couldn't find Course with ID=23 for Project with ID=62
app/controllers/projects_controller.rb:49:in `update'

{...
"project"=>{"title"=>"Sup",
"due_date"=>"2012-01-23",
"course_id"=>"27",                        # THIS IS THE ID OF THE NEW COURSE I WANT
"course_attributes"=>{"name"=>"Calc I",   # THIS IS THE OLD ONE, I don't need this. Why is it passing this?
"number"=>"MATH102",
"user_id"=>"3",
"id"=>"23"},
"description"=>"bla bla bla"},
"commit"=>"Update Project",
"user_id"=>"3",
"id"=>"62"}

So I can see that it's trying to pass in the course_attributes , but it's not actually setting the new course_id . I don't understand why course_attributes is being passed, the other form is blank, and the course_attributes being passed, are the attributes of the old course. I want to set the course_id to be the course_id being passed (27 in this case).

ProjectsController

def new
  @project  = @user.projects.new
  @courses = @user.courses    # Used to populate the collection_select
  @project.build_course       # I was informed I need to use this to get the form_for to work
end

def edit
  @project = Project.find(params[:id])
  @courses = @user.courses    # Used to populate the collection_select
end

def update
  @project = Project.find(params[:id])
  @courses = @user.courses

  if @project.update_attributes(params[:project])
    flash[:notice] = 'Project was successfully updated.'
    redirect_to user_projects_path(@user)
  else
    render :edit
  end
end

Line 49 is the call to update_attributes .

Other Information

project.rb

belongs_to :user
belongs_to :course

attr_accessible :course_id, :course_attributes
accepts_nested_attributes_for :course

course.rb

belongs_to :user
has_many :projects

user.rb

has_many :projects
has_many :courses

So a project has a course_id in the database. I'm currently creating or choosing an existing course on the fly on the Projects#new page. Here's my form for that. I use a JavaScript toggle to alternate between the collection_select and the two text_fields.

projects/new.html.haml

= form_for [@user, @project] do |f|
  # This is shown by default
  = f.collection_select :course_id, @courses, :id, :name, { prompt: true }

  .hidden # This is hidden by default and shown using a toggle
    = f.fields_for :course do |builder|
      = builder.text_field :name, class: 'large', placeholder: 'Ex: Calculus I'
      = builder.label :number, 'Number'
      = builder.text_field :number, class: 'new_project_course_number'
      = builder.hidden_field :user_id, value: current_user.id

Now, if I am on the new project page, and I attach it to a course by choosing an existing course, it will work correctly. The Project will be created, and the course_id will be set correctly.

If I am on the new project page, and I create a course by using my JavaScript toggle, then filling out the Course Name and Course Number , and click Create, then it will also work. The Course will be created, and the Project will be created with the correct course_id .

Sorry for the lengthy post, but I wanted to provide all information I could. Thanks!

UPDATE 1

routes.rb

resources :users do
  resources :projects do
    collection do
      get 'completed'
      match 'course/:course_number' => 'projects#course', as: 'course'
    end
  end

  resources :courses
end

Answer 1

Assuming that your Projects#edit form is similiar to your Projects#new

This is creating the course_attributes in params

  .hidden # This is hidden by default and shown using a toggle
    = f.fields_for :course do |builder|
      = builder.text_field :name, class: 'large', placeholder: 'Ex: Calculus I'
      = builder.label :number, 'Number'
      = builder.text_field :number, class: 'new_project_course_number'
      = builder.hidden_field :user_id, value: current_user.id

That's because if a user has a current course it will create fields for every course.

If you want to be able to build a new course on the fly in edit and new change this line to:

    = f.fields_for :course, @project.build_course(:user => @user) do |builder|

This will build a new course regardless of whether you're in edit or new. (Also you can remove @project.build_course in your controller this way.)

Answer 2

您没有列出您的路线，但是假设设置正确，那么ProjectsController更新应该能够执行以下操作：

@course = Course.find(params[:course_id])