Nested model/form doesn't create an entry

Question

While delving into ruby's nested models I encountered an issue.

Consider the following scenario,

I have the following models:

• Author
• Book

With the following specifications:

class Author < ActiveRecord::Base
  attr_accessible :name
  has_many :books, dependent: :destroy

  accepts_nested_attributes_for :books #I read this is necessary here: http://stackoverflow.com/questions/12300619/models-and-nested-forms

  # and some validations...
end

class Book < ActiveRecord::Base
  attr_accessible :author_id, :name, :year
  belongs_to :author

  #and some more validations...
end

I would like to add a book to an author. Here is my authors_controller:

def new_book
  @author = Author.find(params[:id])
end

def create_book
  @author = Author.find(params[:id])
  if @author.books.create(params[:book]).save
    redirect_to action: :show
  else
    render :new_book
  end
end

And this is the form with which I try doing it:

<h1>Add new book to <%= @author.name %>'s collection</h1>
<%= form_for @author, html: { class: "well" } do |f| %>
    <%= fields_for :books do |b| %>
        <%= b.label :name %>
        <%= b.text_field :name %>
        <br/>
        <%= b.label :year %>
        <%= b.number_field :year %>
    <% end %>
    <br/>
    <%= f.submit "Submit", class: "btn btn-primary" %>
    <%= f.button "Reset", type: :reset, class: "btn btn-danger" %>
<% end %>

When I type in the data and click "submit" it even redirects me to the correct author, but it doesn't save a new record for that author. 当我输入数据并单击“提交”时，它甚至会将我重定向到正确的作者，但不会为该作者保存新记录。 After a lot of research I can't seem to find what I am doing wrong here.

Answer 1

Change authors_controller to:

def new_book
  @author = Author.find(params[:id])
  @book = Book.new
end

Your form to:

<h1>Add new book to <%= @author.name %>'s collection</h1>
<%= form_for ([@author, @book]), html: { class: "well" } do |f| %>

And, routes.rb

resources :authors do
  resources :books
end  

Answer 2

You're missing a couple of things.

Controller:

...
def new_book
  @author = Author.find(params[:id])
  @author.books.build
end
...

View, it is f.fields_for and not just fields_for :

<%= f.fields_for :books do |b| %>
  <%= b.label :name %>
  <%= b.text_field :name %>
  <br/>
  <%= b.label :year %>
  <%= b.number_field :year %>
<% end %>

Answer 3

You also need to add :nested_attributes_for_books on your Author model accessible methods. The create method on you Author controller doesn't need any code additions to get going.

Note: You set the Books controller to render 'books#show' on success. If the app is redirecting you to the author that means the Author controller is handling the creation of the book, unless you set it to redirect to author and not the book.