Ruby on Rails: How to provide a list of items that can be dragged and dropped on each other

In this example, the drag-and-drop action results in submission of a form followed by rendering of a new page.

Preparation

No special preparation is required.

Database

It is assumed only that the database includes a table of items with identifiers.

Model

No modifications to models are required.

View

First, there is a JavaScript function to submit the form upon drag-and-drop:

<script>
  function merge(draggable, droppable, event) {
    document.merge.source.value = draggable.id;
    document.merge.destination.value = droppable.id;
    document.merge.submit();
  }
</script>

Then, there is the form referencing the action to perform upon drag-and-drop. The form tag requires a name for the JavaScript function to work:

<% form_tag('/items/merge', :name => 'merge') do -%>
    <input name="source" type="hidden">
    <input name="destination" type="hidden">
<% end -%>

Each item that can be dragged and dropped on should be in a container with a unique id.

<% for item in @items %>
	<div class=”items” id=”item_<%= item.id %>”>
		<%= item.name %>
	</div>
	<%= draggable_element(“item_” + item.id.to_s, :revert => true) %>
	<%= drop_receiving_element(“item_” + item.id.to_s,
	  :onDrop => “function(drag, drop, e) { merge(drag, drop, e); }”,
	  :hoverclass => “hover”) %>
<% end %>

Controller

The controller includes an action that extracts the IDs of the dragged and dropped-on elements:

def merge
    drag = Summary.find(params[:source].split('_')[1])
    target = Summary.find(params[:destination].split('_')[1])

After performing the necessary actions, the method can render or redirect to the necessary page.

Tags: Technical

Updated at: 5 December 2008 12:12 AM

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