How to implement presence validation for nested model in Rails?

Question

Full source code is here https://github.com/tenzan/postfile

Creating a post working fine.

I have a parent element "Conversation" and its child/nested element "Post".

When I click on "Create Post" with nothing entered, it should throw an error "Body can't be blank".

Instead, it giving another error:

conversation.rb :

class Conversation < ApplicationRecord
  belongs_to :contact
  has_many :posts
end

post.rb :

class Post < ApplicationRecord
  belongs_to :conversation
  belongs_to :author, polymorphic: true
  has_rich_text :body

  validates :body, presence: :true
end

posts_controller.rb :

class PostsController < ApplicationController
    before_action :authenticate_user!
    before_action :set_conversation

    def create
        @post = @conversation.posts.new(post_params)
        @post.author = current_user
        
       respond_to do |format|
           
           if @post.save
            format.html { redirect_to @conversation }
           end
       end
    end

    private
    def set_conversation
        @conversation = Conversation.find(params[:conversation_id])
    end

    def post_params
        params.require(:post).permit(:body)
    end
end

I show all posts within from conversation's show.html.erb :

<p id="notice"><%= notice %></p>

<p>
  <strong>Subject:</strong>
  <%= @conversation.subject %>
</p>

<p>
  <strong>Contact:</strong>
  <%= link_to @conversation.contact.name, @conversation.contact %>
</p>

<%= link_to 'Edit', edit_conversation_path(@conversation) %> |
<%= link_to 'Back', conversations_path %>

<div id="posts">
 <%= render @posts %>
</div>

<%= render partial: "posts/form", locals: { conversation: @conversation, post: Post.new } %>

Posts's partial _form.html.erb :

<%= form_with model: [conversation, post], id: "form" do |form| %>

<div>
 <% form.object.errors.full_messages.each do |message| %>
  <div><%= message %></div>
  <% end %>
</div>

<br>

 <%= form.rich_text_area :body %>

 <%= form.submit %>

<% end %>

Full source code is here https://github.com/tenzan/postfile

Thanks in advance.

Answer 1

You have this block in your posts_controller , which is where your error is arising:

respond_to do |format|           
  if @post.save
    format.html { redirect_to @conversation }
  end
end

Inside a respond_to block, you should have blocks identified by the format type, but you've added an if statement at that top level of the block where Rails is expecting a format.xxx . Move the if outside your respond_to block and you should be fine:

if @post.save
  respond_to do |format|           
    format.html { redirect_to @conversation }
  end
else
  DO SOMETHING WITH THE ERROR
end

(Also NB that you should handle the error if the post doesn't save, even if it's just to say "Sorry, please try again".)