Question

I have no idea why this isn’t working, but I can’t seem to get a complex form to create my necessary join models.

So a site can have many environments, through siteenvs.

site.rb

class Site < ActiveRecord::Base
  has_many :siteenvs, :dependent => :destroy
  has_many :environments, :through => :siteenvs, :uniq => true
  attr_accessible :name, :description, :documentation, :protocol, :port, :siteenvs_attributes
  accepts_nested_attributes_for :siteenvs, :reject_if => proc { |attributes| attributes["environment_id"] == "0"}
end

siteenv.rb

class Siteenv < ActiveRecord::Base
  belongs_to :site
  belongs_to :environment
  validates :site_id, :uniqueness => { :scope => :environment_id }
end

environment.rb

class Environment < ActiveRecord::Base
  has_many :siteenvs, :dependent => :destroy
  has_many :sites, :through => :siteenvs, :uniq => true
end

Pretty standard stuff here. Now here is my controller. What I’m doing is asking the database how many Environments there are, and building that many siteenvs for a new site. This is so that the form will have one checkbox for each environment, so a user can choose whatever they would like.

sites_controller.rb

class SitesController < ApplicationController
  load_and_authorize_resource
  respond_to :html, :xml, :json

  def new 
    @site = Site.new
    Environment.all.each do |env|
      siteenv = @site.siteenvs.build(:environment_id => env.id)
    end 
    respond_with (@site)
  end

  ...

  def create
    @site = Site.new(params[:site])
    if @site.save
      flash[:success] = "New site created."
      respond_with(@site, :location => @site)
    else
      render 'new'
    end
  end
end

And then my new site form looks like this:

sites/new.html.erb

<h1>Create a new site</h1>

<%= form_for(@site) do |f| %>
  <h3>Step 1 - General</h3>
    <table>
      <%= render 'site_fields', :f => f %>
    </table>

  <h3>Step 2 - Environments</h3>
    <div id="environments">
      <ul>
        <%= f.fields_for :siteenvs do |builder| %>
          <% environment = Environment.find(builder.object.environment_id) %>
          <li><%= builder.check_box :environment_id, { :checked => false, :class => "s_environment_checkbox", :env => environment.name, :domain => environment.domain }, builder.object.environment_id %>
          <%= builder.label :environment_id, "#{environment.name}" %>
          </li>
        <% end %>
      </ul>
    </div>

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

So what happens is that my form renders correctly, and all the HTML attributes appear to be correct. The value of the checkboxes is the ID of the corresponding environment, and the names all appear to be happy Rails generated HTML:

form HTML

<li>
    <input name="site[siteenvs_attributes][0][environment_id]" type="hidden" value="0">
    <input class="s_environment_checkbox" domain="example.com" env="env1" id="site_siteenvs_attributes_0_environment_id" name="site[siteenvs_attributes][0][environment_id]" type="checkbox" value="1">
</li>

However, unless you mark every single checkbox, I get an error referring to some method on the siteenvs model. I imagine this is due to the fact that submitted parameters are referencing an environment_id that doesn’t exist (0), but I would think that rails would ignore this. In fact, I’m not even sure why those environment_ids are being submitted if they aren’t checked! Here is some example output from when I only chose one checkbox, out of 5:

submitted params

{"utf8"=>"✓",
"authenticity_token"=>"Q1zdbb/ibcJrKb2FYf45o+Q43o2PZm1UU75dngis1UE=",
"site"=>{"name"=>"bob",
"description"=>"",
"documentation"=>"",
"protocol"=>"http",
"port"=>"80",
"siteenvs_attributes"=>{"0"=>{"environment_id"=>"1",
"url"=>""},
"1"=>{"environment_id"=>"0"},
"2"=>{"environment_id"=>"0"},
"3"=>{"environment_id"=>"0"},
"4"=>{"environment_id"=>"0"}}},
"commit"=>"Finish"}

So I have no idea where that 0 came from, nor why the unselected checkboxes are even being including in the params. Any ideas?

Answer 1

This is straight from the documentation for the check_box method for forms:

Returns a checkbox tag tailored for accessing a specified attribute
(identified by method) on an object assigned to the template
(identified by object). This object must be an instance object
(@object) and not a local object. It’s intended that method returns an
integer and if that integer is above zero, then the checkbox is
checked. Additional options on the input tag can be passed as a hash
with options. The checked_value defaults to 1 while the default
unchecked_value is set to 0 which is convenient for boolean values.

Gotcha

The HTML specification says unchecked check boxes are not successful,
and thus web browsers do not send them. Unfortunately this introduces
a gotcha: if an Invoice model has a paid flag, and in the form that
edits a paid invoice the user unchecks its check box, no paid
parameter is sent. So, any mass-assignment idiom like

@invoice.update_attributes(params[:invoice])

wouldn’t update the flag.

From the params of your code I see that the four environment_id => "0" are the unchecked value of the checkbox. You will want to filter out those when you handle the data.