Ruby-on-rails – Rails 3: How to create a new nested resource

ruby-on-railsruby-on-rails-3

The Getting Started Rails Guide kind of glosses over this part since it doesn't implement the "new" action of the Comments controller. In my application, I have a book model that has many chapters:

class Book < ActiveRecord::Base
  has_many :chapters
end

class Chapter < ActiveRecord::Base
  belongs_to :book
end

In my routes file:

resources :books do
  resources :chapters
end

Now I want to implement the "new" action of the Chapters controller:

class ChaptersController < ApplicationController
  respond_to :html, :xml, :json

  # /books/1/chapters/new
  def new
    @chapter = # this is where I'm stuck
    respond_with(@chapter)
  end

What is the right way to do this? Also, What should the view script (form) look like?

Best Answer

First you have to find the respective book in your chapters controller to build a chapter for him. You can do your actions like this:

class ChaptersController < ApplicationController
  respond_to :html, :xml, :json

  # /books/1/chapters/new
  def new
    @book = Book.find(params[:book_id])
    @chapter = @book.chapters.build
    respond_with(@chapter)
  end

  def create
    @book = Book.find(params[:book_id])
    @chapter = @book.chapters.build(params[:chapter])
    if @chapter.save
    ...
    end
  end
end

In your form, new.html.erb

form_for(@chapter, :url=>book_chapters_path(@book)) do
   .....rest is the same...

or you can try a shorthand

form_for([@book,@chapter]) do
    ...same...

Hope this helps.

Related Solutions

Ruby-on-rails – Rails: How to rename a database column in a Ruby on Rails migration

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

script/generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

For Rails 3.1 use:

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

Then just db:migrate as usual or however you go about your business.

For Rails 4:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Ruby-on-rails – How to get the current absolute URL in Ruby on Rails

For Rails 3.2 or Rails 4+

You should use request.original_url to get the current URL. Source code on current repo found here.

This method is documented at original_url method, but if you're curious, the implementation is:

def original_url
  base_url + original_fullpath
end

For Rails 3:

You can write "#{request.protocol}#{request.host_with_port}#{request.fullpath}", since request.url is now deprecated.

For Rails 2:

You can write request.url instead of request.request_uri. This combines the protocol (usually http://) with the host, and request_uri to give you the full address.