Rails3 Nested Attributes Using Parent Values in Save Action

Question

I've got a simple nested form working in my rails3 application. I'm trying to work out how to save a value from the parent model into the child when saving.

class Radcheck < ActiveRecord::Base
  set_table_name 'radcheck'
  attr_accessible :attribute_name, :username, :value, :op
  belongs_to :raduser  
end

class Raduser < ActiveRecord::Base
  has_many :radcheck, :dependent => :destroy
  accepts_nested_attributes_for :radcheck  
end

And my form:

<%= form_for @raduser do |f| %>  
  <p>  
    <%= f.label :username %><br />  
    <%= f.text_field :username %>  
  </p>  
  <%= f.fields_for :radcheck do |builder| %>  
  <li>  
    <%= builder.label :attribute_name %><%= builder.text_field :attribute_name %>  

  </li>  
  <% end %>  
  <p><%= f.submit "Submit" %></p>  
<% end %>

What I want to do is save the Raduser.username value in to the radcheck table on save. For each record.

I've tried putting something in the controller but that wasn't really working for us.

-- Update --

In my radcheck controller, I've tried this (as a test) but the values don't save.

def create
      @radcheck = Radcheck.new(params[:radcheck])
      @radcheck.username = '123'
      respond_to do |format|
        if @radcheck.save

          format.html { redirect_to @radcheck, notice: 'Radcheck was successfully created.' }
          format.json { render json: @radcheck, status: :created, radcheck: @radcheck }
        else
          format.html { render action: "new" }
          format.json { render json: @radcheck.errors, status: :unprocessable_entity }
        end
      end
    end

Have also tried in radusers but that gave error.

It seems that username is a column of radcheck table(looking at the model and controller code)..In your view code, it is treated like a column of radusers table — rubyprince
– rubyprince, Commented Nov 21, 2011 at 12:47
@rubyprince that's right - they both have that column - am working with a legacy db and can't update — Jenny Blunt
– Jenny Blunt, Commented Nov 21, 2011 at 13:14

Ian Eccles · Accepted Answer · 2011-11-21 14:23:06Z

3

It looks like the controller code you posted is for the Radcheck controller, correct? If so, the form you have also posted will be using the create action of the RaduserController class, not the one from RadcheckController. This would explain why you aren't seeing the username '123' in the radcheck rows.

If the username field is the same between parent and child, a common way to sync these two up would be with an observer or a before_save callback. I'll outline the before_save method below:

class Radcheck < ActiveRecord::Base
  set_table_name 'radcheck'
  attr_accessible :attribute_name, :username, :value, :op
  belongs_to :raduser

  before_save :sync_usernames

private

  def sync_usernames
    self.username = self.raduser.username
  end
end

I've tested this with Rails 3.1 and it works; however, I know I have run into issues accessing parent models within a child model in previous versions of Rails. In those cases, I had to put the before_save action on the parent model, and have it iterate over each child, setting the appropriate attributes that way.

answered Nov 21, 2011 at 14:23

Ian Eccles

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4 Comments

Jenny Blunt Over a year ago

I'm on 3.1.1 - I get an insert in the log for raduser but it doesn't look like anything's going in to radcheck. J

Jenny Blunt Over a year ago

Strangely, it now works. Bit concerned I didn't do much to get it going. Thanks for sorting :)

Ian Eccles Over a year ago

It does seem odd that it would initially not work, and then suddenly start working. Without knowing more about your setup, I can only make guesses as to why that happened. At any rate, glad to hear it's working for you now.

Jenny Blunt Over a year ago

Not a big fan of intermittent issues either!! thanks again :)

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