Question

I don’t know which is the best or right way to make something, so I’m looking for suggestions.

Stage:
I am using Rails 3 to make some web app.
Imaging two models: Canvas and Zone.
A canvas object intents to be a square in which there will be four zone‘s (north, south, east and west).
Each zone has these attributes: text:string and rgb_color:string.
I want to render a HTML form in which user must capture a Canvas registry, in other words, in this form will have four groups of zones fields.

Problem:
How can I capture all of them in one HTML form?

If I would have only one zone I can do something like this:

<%= form_for(@zone) do |f| %>
  <div class="field">
    <%= f.label :text %><br />
    <%= f.text_field :text %>
  </div>
  <div class="field">
    <%= f.label :rgb_color %><br />
    <%= f.text_field :rgb_color %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

But how should I do it with four zones?

Answer 1

You can do this with accepts_nested_attributes_for and fields_for:

Model:

class Canvas < ActiveRecord::Base
  has_many :zones
  accepts_nested_attributes_for :zones
end

Controller:

class CanvasesController < ApplicationController
  def new
    @canvas = Canvas.new
    4.times { @canvas.zones.build }
  end
end

View:

<%= form_for(@canvas) do |f| %>
  <%= f.fields_for :zones do |zone| %>
    <div class="field">
      <%= zone.label :text %><br />
      <%= zone.text_field :text %>
    </div>
    <div class="field">
      <%= zone.label :rgb_color %><br />
      <%= zone.text_field :rgb_color %>
    </div>
  <% end %>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

For more details and explanation have a look at this:

• Nested Model Form Part 1
• Nested Model Form Part 2