== Message Block

Implements the common view pattern by which a list of messages are shown at the top, 
often a combination of flash messages and ActiveRecord validation issues on one or more models.  
This allows for a nice, stylized block of messages at the top of the page with icons 
indicating what type of message it is (error, confirmation, warning, etc.)

This view helper acts as a replacement for error_messages_for by taking error messages 
from your models and combing them with flash messages (multiple types such as error, confirm, etc.) 
and outputting them to your view.  This gem comes with an example stylesheet and images.

== Installation

This gem is testing working with Rails 3.0 only!

Include the gem using bundler in your Gemfile:

  gem "message_block"

Then run the rake task to install the static files:

  rake message_block:install

Then be sure to include the CSS definitions:

  <%= stylesheet_include_tag "message_block" %>

== Usage

Once you install this, you should now have a set of images at public/images/message_block and 
a basic stylesheet installed at public/stylesheets/message_block.css.  Then you can use 
the helper <tt><%= message_block %></tt>:

The first argument specifies a hash options:

* <tt>:on</tt> - specifies one or many model names for which to check error messages.
* <tt>:model_error_type</tt> - specifies the message type to use for validation errors; defaults to 'error'
* <tt>:flash_types</tt> - specifies the keys to check in the flash hash.  Messages will be grouped in ul 
  lists according to this type.  Defaults to: %w(back confirm error info warn)
* <tt>:html</tt> - Specifies HTML options for the containing div
* <tt>:id</tt> - Specifies ID of the containing div; defaults to 'message_block'
* <tt>:class</tt> - Specifies class name of the containing div; defaults to nothing.
* <tt>:container</tt> - specifies which block-level element to contain the errors (defaults to :div).

=== Example
Imagine you have a form for entering a user and a comment:

  <%= message_block :on => [:user, :comment] %>

Imagine also you set these flash variables in the controller:
  class CommentsController
    def create
      flash.now[:error] = "Error A"
      flash.now[:confirm] = "Confirmation A"  # Note you can use different types
      flash.now[:warn] = ["Warn A", "Warn B"]  # Can set to an array for multiple messages
    end
  end

And let's say that you want to show these messages but also show the validation issues 
given that both user and comment fail ActiveRecord validation:

  <div id="message_block" class="message_block">
    <ul class="error">
      <li>Error A</li>
      <li>User first name is required.</li>
      <li>Comment contents is required.</li>
    </ul>
    <ul class="confirm">
      <li>Confirmation A</li>
    </ul>
    <ul class="warn">
      <li>Warn A</li>
      <li>Warn B</li>
    </ul>
  </div>

=== Ajax & JavaScript Integration

Sometimes you'll want to use the message block pattern within JavaScript.  Wouldn't it be nice to just populate 
the message_block DOM tree based on a JavaScript object not unlike Rails flash?

Included in the plugin is a Prototype JS implementation to make this easier.  Note that this file is *not* automatically 
copied when the plugin is installed.  Currently this only works with prototype, but will be converted to jQuery before long:
  
  assets/javascripts/message_block.js

Example Usage:
  
  <div id="something">
    <%= message_block :on => :job %>
  </div>
  
  <script type="text/javascript">
    document.observe('dom:loaded', function() {
      message_block = new MessageBlock('message_block');  // Default ID is message_block, being explicit
      
      // Updates with two errors and one confirmation
      message_block.update({
        error: ['Error One', 'Error Two'],
        confirm: ['Confirmation Message']
      });
      
      // Clears the message block
      message_block.clear();
      
      // Same as above...
      message_block.update({});
    });
  </script>

This could be useful if you're interacting with stuff via Ajax, for example:

  # In Controller
  wants.json do
    render :status => :unprocessable_entity, :json => { 'error' => @job.errors.full_messages }
  end
  
  # JavaScript Ajax
  new Ajax.Request("/jobs", {
    method: 'get',
    
    onFailure: function(transport) {
      this.message_block.update(transport.responseJSON);
    },
    
    onSuccess: function(transport) {
      this.message_block.clear();
      
      // Do something...
    }
  });