Simple_Form Association with has_many :through extra field

Question

I have two models, Developers and Tasks,

class Developer < ActiveRecord::Base
  attr_accessible :address, :comment, :email, :name, :nit, :phone, :web
  has_many :assignments
  has_many :tasks, :through => :assignments
end

class Task < ActiveRecord::Base
  attr_accessible :description, :name, :sprint_id, :developer_ids
  has_many :assignments
  has_many :developers, :through => :assignments
end

class Assignment < ActiveRecord::Base
  attr_accessible :accomplished_time, :developer_id, :estimated_time, :status, :task_id
  belongs_to :task
  belongs_to :developer
end

im taking care of the relation by adding an Assignment table, so i can add many developers to one task in particular, now i would also like to be able to manipulate the other fields i added to the joining table like the 'estimated_time', 'accomplished_time'... etc... what i got on my Simple_form is `

<%= simple_form_for [@sprint,@task], :html => { :class => 'form-horizontal' } do |f| %>
  <%= f.input :name %>
  <%= f.input :description %>
  <%= f.association :developers, :as => :check_boxes %>

  <div class="form-actions">
    <%= f.button :submit, :class => 'btn-primary' %>
    <%= link_to t('.cancel', :default => t("helpers.links.cancel")),
                project_sprint_path(@sprint.project_id,@sprint), :class => 'btn' %>
  </div>
<% end %>`

This only allows me to select the developers, i want to be able to modify the estimated_time field right there.

Any Suggestions?

Answer 1

I love how simple-form has the association helpers, making it really easy in some cases. Unfortunately, what you want you cannot solve with just simple-form.

You will have to create assignments for this to work.

There are two possible approaches.

For both you will have to add the following to your model:

class Task
  accepts_nested_attributes_for :assignments
end

Note that if you are using attr_accesible, you should also add assignments_attributes to it.

The easy approach

Suppose you know how many assignments, maximally, a task would have. Suppose 1 for simplicity.

In your controller, write

def new
  @task = Task.build
  @task.assignments.build
end

This will make sure there is one new assignment.

In your view write:

= simple_form_for [@sprint,@task], :html => { :class => 'form-horizontal' } do |f| 
  = f.input :name 
  = f.input :description 

  = f.simple_fields_for :assignments do |assignment|
    = assignment.association :developer, :as => :select
    = assignment.estimated_time

  .form-actions
    = f.button :submit, :class => 'btn-primary'
    = link_to t('.cancel', :default => t("helpers.links.cancel")),
                project_sprint_path(@sprint.project_id,@sprint), :class => 'btn'

The problem with this approach: what if you want more than 1, 2 or 3?

Use cocoon

Cocoon is a gem that allows you to create dynamic nested forms.

Your view would become:

= simple_form_for [@sprint,@task], :html => { :class => 'form-horizontal' } do |f| 
  = f.input :name 
  = f.input :description 

  = f.simple_fields_for :assignments do |assignment|
    = render `assignment_fields`, :f => assignment
  .links
    = link_to_add_association 'add assignment', f, :assignments

  .form-actions
    = f.button :submit, :class => 'btn-primary'
    = link_to t('.cancel', :default => t("helpers.links.cancel")),
                project_sprint_path(@sprint.project_id,@sprint), :class => 'btn'

And define a partial _assignment_fields.html.haml :

.nested_fields
  = f.association :developer, :as => :select
  = f.estimated_time
  = link_to_remove_association 'remove assignment', f

Hope this helps.