My first views field handler for Drupal 7

Few month ago I developed  a simple module called Commerce Order2pdf and then I also added custom tokens as you can read from this post Custom token creation for Drupal 7 and now I reviewed this module a bit and planned to add views field handler (This means I can create custom view with download links). 

So how did I implemented this?

First step was to edit commerce_order2pdf.module file and add hook_views_api. So I could start working with views.

/**
 * Implements hook_views_api().
 */
function commerce_order2pdf_views_api() {
  return array(
    'api' => 3,
    'path' => drupal_get_path('module', 'commerce_order2pdf') . '/includes/views',
  );
}

Next one was to create subdirectories includes/views into my commerce_order2pdf folder (module folder).

After this I had to tell views about my data structure.
So I did created new file /includes/views/commerce_order2pdf.views.inc and added hook_views_data.

/**
 * Implements hook_views_data()
 */
function commerce_order2pdf_views_data() {
  $data = array();
  $data['commerce_order']['order2pdf_link'] = array(
    'field' => array(
      'title' => t('Download pdf order'),
      'help' => t('Provide a simple link to download the order.'),
      'handler' => 'commerce_order2pdf_handler_field_order_pdf_link',
    ),
  );
  return $data;
 }

In this array I did extended commerce_order group and added field handler class callback.

Now we will add a new file commerce_order2pdf_handler_field_order_pdf_link.inc to includes/views folder.

/**
 * Field handler to present an order pdf download link.
 */
class commerce_order2pdf_handler_field_order_pdf_link extends commerce_order_handler_field_order_link {
  function construct() {
    parent::construct();
  }

  function render($values) {
    $order = commerce_order_new();
    $order->order_id = $this->get_value($values, 'order_id');
    // Add hash key for a download link.
    $hash = hash('md5', $order->order_id . $values->commerce_order_created);

    $text = !empty($this->options['text']) ? $this->options['text'] : t('Download');
    return l($text, "order2pdf/{$order->order_id}/{$hash}");
  }
}

My last step is to say Drupal about these files in commerce_order2pdf.info

For this step I will just add two rows to my .info file. 

files[] = includes/views/commerce_order2pdf.views.inc
files[] = includes/views/commerce_order2pdf_link_handler.inc

Now you can add views download field to your view. (If you make thses changes after you enabled your module then you can just clear caches and it will work).

Edit 13. April 2013 
Just found a good videos