add support for sorting nested forms

README.markdown

@@ -16,6 +16,8 @@ This project is not related to [Apache Cocoon](http://cocoon.apache.org/)
 This gem uses jQuery, it is most useful to use this gem in a rails3
 project where you are already using jQuery.
 
+Sortable form support requires jQuery UI.
+
 Furthermore i would advice you to use either formtastic or simple_form.
 
 I have a sample project where I demonstrate the use of cocoon with formtastic.
@@ -37,6 +39,13 @@ asset_pipeline
 //= require cocoon
 ````
 
+If you also want to be able to sort nested forms, ordering them on a particular field, add `cocoon/ordered`:
+
+``` ruby
+//= require cocoon
+//= require cocoon/ordered
+```
+
 ### Rails 3.0.x
 
 If you are using Rails 3.0.x, you need to run the installation task (since rails 3.1 this is no longer needed):
@@ -125,6 +134,53 @@ That is all there is to it!
 
 There is an example project on github implementing it called [cocoon_formtastic_demo](https://github.com/nathanvda/cocoon_formtastic_demo).
 
+Or, you can use the Formtastic `cocoon` field type to wrap up much of the boilerplate of the wrapper and
+add association button:
+
+``` haml
+= f.inputs do
+  = f.input :name
+  = f.input :description
+  %h3 Tasks
+  #tasks
+    = f.input :tasks, :as => :cocoon
+  = f.actions do
+    = f.action :submit
+```
+
+#### Sortable forms
+
+Say you have a set of nested models that are ordered arbitrarily:
+
+``` ruby
+class Task < ActiveRecord::Base
+  belongs_to :project
+
+  default_scope :order => 'order ASC'
+end
+```
+
+You want users to be able to sort those
+models via the UI. You can do this by including `cocoon/ordered` and specifying the sort field in the Formtastic
+input call:
+
+``` haml
+= f.input :tasks, :as => :cocoon, :ordered_by => :order
+```
+
+Add the order field as a hidden field in the nested form:
+
+``` haml
+.nested-fields
+  = f.inputs do
+    = f.input :description
+    = f.input :done, :as => :boolean
+    = f.input :order, :as => :hidden
+    = link_to_remove_association "remove task", f
+```
+
+The order field will now be filled in correctly when new models are added and when the models are sorted.
+
 ### Using simple_form
 
 Inside our `projects/_form` partial we then write:

app/assets/javascripts/cocoon.js

@@ -51,14 +51,14 @@
 
     var contentNode = $(new_content);
 
-    insertionNode.trigger('cocoon:before-insert');
+    insertionNode.trigger('cocoon:before-insert', contentNode);
 
     // allow any of the jquery dom manipulation methods (after, before, append, prepend, etc)
     // to be called on the node.  allows the insertion node to be the parent of the inserted
     // code and doesn't force it to be a sibling like after/before does. default: 'before'
     insertionNode[insertionMethod](contentNode);
 
-    insertionNode.trigger('cocoon:after-insert');
+    insertionNode.trigger('cocoon:after-insert', contentNode);
   });
 
   $('.remove_fields.dynamic').live('click', function(e) {

app/assets/javascripts/cocoon/ordered.js

@@ -0,0 +1,29 @@
+//= require jquery-ui
+//
+(function($) {
+  $(function() {
+    $('li[data-ordered_by]').each(function(index, element) {
+      var field = $(element).data('ordered_by');
+      var fieldSearch = "[name*='[" + field + "]']"
+
+      $(element).sortable({
+        items: '.nested-fields',
+        stop: function(e, ui) {
+          $(element).find(fieldSearch).each(function(index, element) {
+            $(element).val(index);
+          });
+        }
+      });
+
+      $(element).bind('cocoon:after-insert', function(e, node) {
+        var nextOrder = 0;
+
+        $(element).find(fieldSearch).each(function() {
+          nextOrder = Math.max(nextOrder, Number($(this).val()) + 1);
+        });
+
+        $(node).find(fieldSearch).val(nextOrder)
+      });
+    });
+  });
+})(jQuery);

app/assets/stylesheets/cocoon/active_admin.css.scss

@@ -18,5 +18,12 @@ li.cocoon {
   .links a {
     @extend .button;
   }
+
+  &.ui-sortable {
+    fieldset {
+      border-top: solid #777 12px;
+      cursor: move;
+    }
+  }
 }
 

lib/cocoon/formtastic/cocoon_input.rb

@@ -18,7 +18,12 @@ class CocoonInput
       template.link_to_add_association template.t('.add'), builder, method
     end
 
-    template.content_tag(:li, output.join('').html_safe, :class => 'input cocoon')
+    data = { :class => 'input cocoon' }
+    if options[:ordered_by]
+      data['data-ordered_by'] = options[:ordered_by]
+    end
+
+    template.content_tag(:li, output.join('').html_safe, data)
   end
 end