== Undo helper plugin for Rails

Rails controller with a _create_ action that creates a new record, a _delete_ action that will undo it, and a _before_filter_ that removes undo actions from the stack:

  # Remove undo action from stack.
  before_filter do |controller|
      controller.undo.pop(controller.params) if controller.params[:undo]
  end

  # The create action creates a new record, the undo action deletes it.
  def create()
      # Do something useful here
      record = Record.create(@params)
      # If this is not an undo, add an undo action to delete the record.
      unless @params[:undo]
          undo.push ("Delete newly created record",
              :action=>"delete", :id=>record.id)
      end
      # Render page (see below).
      . . .
  end

  def delete()
     . . .
  end

Line from a view that creates a wrapper element and renders the undo form and button:

  <div id="undo"><%= undo.render %></div>

Using RJS to instruct the browser to update the undo button without reloading:

  render :update do |page|
      page["undo"].replace_html undo.render
  end


== License

Copyright (c) 2006 Assaf Arkin, under Creative Commons Attribution and/or MIT License

Developed for http://co.mments.com

Code and documention: http://labnotes.org