rails nasted model form - ruby-on-rails

Question

I have model association like this
post.rb
title:string description:text
class Post < ActiveRecord::Base
belongs_to :user
has_many :items
accepts_nested_attributes_for :items
end
item.rb
post_id:integer order:integer
class Item < ActiveRecord::Base
belongs_to :post
has_one :link
has_one :movie
has_one :photo
has_one :quate
end
link, movie, photo, quate.rb
link.rb : item_id:integer url:string url-text:string
movie.rb : item_id:integer youtube-url:string
photo.rb : item_id:integer image:string comment:string title:string
quate.rb : item_id:integer quate:string q-url:string q-title:string
belongs_to :item
I want to build user-post application by ruby on rails.
Item model has order column ,so user can choose and add whatever movie, link , photo to build there own post.
How can I build form for these nasted models?

Answer 1

This might not be as defined as you need; I'll delete if required.
You have a huge antipattern with your belongs_to models. They look like they represent a single data-set, and I would merge them into the Item model, using an enum to differentiate their state:
#app/models/item.rb
class Item < ActiveRecord::Base
#schema id | post_id | state | url | title | comment | created_at | updated_at
belongs_to :post
enum state: [:link, :movie, :photo, :quate]
end
This will give you the ability to create instances of Item, which you can then assign different "states":
#item = Item.new
#item.state = :link
Although it means changing your pattern, it gives you the ability to store items for each post directly (instead of having to append them with another model):
#app/controllers/posts_controller.rb
class PostsController < ApplicationController
def new
#post = Post.new
#post.items.build
end
def create
#post = Post.new post_params
#post.save
end
private
def post_params
params.require(:post).permit(items_attributes: [:state, :url, :title, :comment])
end
end
#app/views/posts/new.html.erb
<%= form_for #post do |f| %>
<%= f.fields_for :items do |i| %>
<%= i.select :state, Item.states.keys.map {|role| [role.titleize,role]}) %>
<%= i.text_field :url %>
<%= i.text_field :title %>
<%= i.text_field :comment %>
<% end %>
<%= f.submit %>
<% end %>
You also need to make sure you have accepts_nested_attributes_for in your Post model:
#app/models/post.rb
class Post < ActiveRecord::Base
has_many :items
accepts_nested_attributes_for :items
end