Rails Form Object with Virtus: has_many association

Question

I am having a tough time figuring out how to make a form_object that creates multiple associated objects for a has_many association with the virtus gem.

Answer 1

You have an issue because you haven't whitelisted any attributes under :emails. This is confusing, but this wonderful tip from Pat Shaughnessy should help set you straight.

This is what you're looking for, though:

params.require(:user_form).permit(:name, { emails: [:email_text, :id] })

Note the id attribute: it's important for updating the records. You'll need to be sure you account for that case in your form objects.

If all this form object malarkey with Virtus gets to be too much, consider Reform. It has a similar approach, but its raison d'etre is decoupling forms from models.

---

You also have an issue with your form… I'm not sure what you were hoping to achieve with the syntax you're using, but if you look at your HTML you'll see that your input names aren't going to pan out. Try something more traditional instead:

<%= f.fields_for :emails do |ff| %>
  <%= ff.text_field :email_text %>
<% end %>

With this you'll get names like user_form[emails][][email_text], which Rails will conveniently slice and dice into something like this:

user_form: { 
  emails: [
    { email_text: '...', id: '...' },
    { ... }
  ]
}

Which you can whitelist with the above solution.

Answer 2

The problem is that the format of the JSON being passed to UserForm.new() is not what is expected.

The JSON that you are passing to it, in the user_form_params variable, currently has this format:

{  
   "name":"testform",
   "emails":{  
      "0":{  
         "email_text":"email1@test.com"
      },
      "1":{  
         "email_text":"email2@test.com"
      },
      "2":{  
         "email_text":"email3@test.com"
      }
   }
}

UserForm.new() is actually expecting the data in this format:

{  
   "name":"testform",
   "emails":[   
       {"email_text":"email1@test.com"}, 
       {"email_text":"email2@test.com"},  
       {"email_text":"email3@test.com"}
   }
}

You need to change the format of the JSON, before passing it to UserForm.new(). If you change your create method to the following, you won't see that error anymore.

  def create
    emails = []
    user_form_params[:emails].each_with_index do |email, i| 
      emails.push({"email_text": email[1][:email_text]})
    end

    @user_form = UserForm.new(name: user_form_params[:name], emails: emails)

    if @user_form.save
      redirect_to @user, notice: 'User was successfully created.' 
    else
      render :new 
    end
  end

Answer 3

I would just set the emails_attributes from user_form_params in the user_form.rb as a setter method. That way you don't have to customize the form fields.

Complete Answer:

Models:

#app/modeles/user.rb
class User < ApplicationRecord
  has_many :user_emails
end

#app/modeles/user_email.rb
class UserEmail < ApplicationRecord
  # contains the attribute: #email
  belongs_to :user
end

Form Objects:

# app/forms/user_form.rb
class UserForm
  include ActiveModel::Model
  include Virtus.model

  attribute :name, String

  validates :name, presence: true
  validate  :all_emails_valid

  attr_accessor :emails

  def emails_attributes=(attributes)
    @emails ||= []
    attributes.each do |_int, email_params|
      email = EmailForm.new(email_params)
      @emails.push(email)
    end
  end

  def save
    if valid?
      persist!
      true
    else
      false
    end
  end


  private

  def persist!
    user = User.new(name: name)
    new_emails = emails.map do |email|
      UserEmail.new(email: email.email_text)
    end
    user.user_emails = new_emails
    user.save!
  end

  def all_emails_valid
    emails.each do |email_form|
      errors.add(:base, "Email Must Be Present") unless email_form.valid?
    end
    throw(:abort) if errors.any?
  end
end 


# app/forms/email_form.rb
# "Embedded Value" Form Object.  Utilized within the user_form object.
class EmailForm
  include ActiveModel::Model
  include Virtus.model

  attribute :email_text, String

  validates :email_text,  presence: true
end

Controller:

# app/users_controller.rb
class UsersController < ApplicationController

  def index
    @users = User.all
  end

  def new
    @user_form = UserForm.new
    @user_form.emails = [EmailForm.new, EmailForm.new, EmailForm.new]
  end

  def create
    @user_form = UserForm.new(user_form_params)
    if @user_form.save
      redirect_to users_path, notice: 'User was successfully created.'
    else
      render :new
    end
  end

  private
    def user_form_params
      params.require(:user_form).permit(:name, {emails_attributes: [:email_text]})
    end
end

Views:

#app/views/users/new.html.erb
<h1>New User</h1>
<%= render 'form', user_form: @user_form %>


#app/views/users/_form.html.erb
<%= form_for(user_form, url: users_path) do |f| %>

  <% if user_form.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(user_form.errors.count, "error") %> prohibited this User from being saved:</h2>

      <ul>
      <% user_form.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %>
    <%= f.text_field :name %>
  </div>


  <%= f.fields_for :emails do |email_form| %>
    <div class="field">
      <%= email_form.label :email_text %>
      <%= email_form.text_field :email_text %>
    </div>
  <% end %>


  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>