Rails, populate database with associated models on one form

Question

I have looked at various answers to similar questions and haven't quite cracked it. A wine model is defined with has_one :register, :dependent => :destroy and rightly or wrongly I have added accepts_nested_attributes_for :register. A register is defined with belongs_to :wine.

The code within wines_controller.rb for create is:

def new
  @wine = Wine.new
  @register = Register.new

def create
  @wine = Wine.new(wine_params)
  @register = @wine.registers.build(register_params)
  respond_to do |format|
    if @wine.save 
    #success
    else
      format.json { render json: @wine.errors, status: :unprocessable_entity }
      format.json { render json: @register.errors, status: :unprocessable_entity }
    end
  end 
end

My form for creating a new wine has the following code:

<%= simple_form_for @wine do |f| %>  
# various working elements
<div class="field">
  <% f.fields_for :register do |r| %>
    <%= r.label :short_name %>
    <%= r.text_field :short_name %>
    <%= r.label :barcode %>
    <%= r.text_field :barcode %>
  <% end %>
</div>

When this form is called up no fields are created from the f.fields_for command but this block is executed because I can add test buttons within it to prove it is accessed.

If I try to create a wine I get the following error message:

undefined method `registers' for #<Wine:0x007f1204375330> Did you mean? register register= register_id

I believe that using .build is there to ensure data integrity: I don't want to create a wine that does not have a corresponding register. I have tried thinking about it nested attributes but that seems to be considered a bad plan by many. This current approach feels correct but I think I am missing some understanding of syntax at the very least.

At a later date it will be necessary to have other models linked to register that will not be associated to wines. I was considering a similar approach but I am happy to be told to rethink!

David · Accepted Answer · 2016-10-12 21:23:22Z

2

If I understand you correctly you have 2 issues:

Firstly fields for register aren't being displayed - this is partly because @wine.register is nil.

You should change your new action to:

def new
  @wine = Wine.new
  @wine.register = Register.new

In addition because you are using simple_form_for you will need to use simple_fields_for instead of fields_for

Your second issue that results in the exception tells you everything... you are trying to access @wine.registers, and not @wine.register

Change in your create method to:

  @register = @wine.register.build(register_params)

This will fix that issue ... however ... all you really need to do is build the @wine object from your params - your params should be configured to permit the right nested attributes - if it is set up correctly the register object will also be built when building the @wine object.

Your model is already set to accept_nested_attributes and thus will also validate and save the register object when calling @wine.save - no need to explicitly save the register object.

You should have something like:

def wine_params
    params.require(:wine).permit(
          :attribute1, :attribute2,
          register_attributes: [:id, :short_name, :barcode])
end

edited Oct 12, 2016 at 21:23

answered Oct 12, 2016 at 19:54

David

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9 Comments

fatherdamo Over a year ago

OK, thanks for the input. The first adjustment you suggest gives rise to ` ActiveModel::MissingAttributeError in WinesController#new ` and can't write unknown attribute 'wine_id'

fatherdamo Over a year ago

That error arises if I try to create a new wine entry

David Over a year ago

could you clarify ... are we talking about the @wine.register = Register.new line? If so then check your Register table ... it should have a wine_id reference

fatherdamo Over a year ago

The table wines does indeed have have a column wine_id, automatically created by Rails. The error message is pointing to the line @wine.register = Register.new

fatherdamo Over a year ago

I tried adding wine_id into the attributes of register` but happily that didn't fix it. I would only have been confused if it had!

|

Emmanuel Mtali · Accepted Answer · 2016-10-13 20:00:41Z

0

Try this

Wine and Register models

class Wine < ApplicationRecord
    has_one :register, inverse_of: :wine,  :dependent => :destroy
    accepts_nested_attributes_for :register
end

class Register < ApplicationRecord
    belongs_to :wine, inverse_of: :register
    validates_presence_of :wine
end

Wines Controller

class WinesController < ApplicationController
  def new
    @wine = Wine.new
    @wine.build_register
  end


  def create
    @wine = Wine.new(wine_params)

    if @wine.save
        redirect_to @wine
    else
        render :new
    end
  end

  private
    def wine_params
        params.require(:wine).permit(:name, register_attributes: [:simple_name])
    end
end

My wine_params are specific for

rails g model wine name:string
rails g model register name:string wine_id:integer

Lastly wine form should look like this

<%= form_for @wine do |f|%>
    <p>
        <%= f.label :name%>
        <%= f.text_field :name%>
    </p>

    <%= f.fields_for :register do |r|%>
    <p>
        <%= r.label :simple_name%>
        <%= r.text_field :simple_name%>
    </p>    
    <% end %>

    <%= f.submit %>
<% end %>

So you can modify wine_params and form partial for your application specifics

edited Oct 13, 2016 at 20:00

answered Oct 13, 2016 at 19:55

Emmanuel Mtali

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2 Comments

Emmanuel Mtali Over a year ago

register will be saved automatically when you create wine

Emmanuel Mtali Over a year ago

Also you can use simple_form_for and simple_fields_for instead of form_for and fields_for

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