Question

I am using php 5.3.3 and developing a MVC webapp using codeigniter. The code I am trying to refactor is basically bunch of:

$this->db->trans_start();
    // do some db updates
    $this->db->update(...);
    $this->db->update(...);
$this->db->trans_complete();

if ( $this->db->trans_status() == FALSE ) {
    $this->handle_db_error();
}

so I have a few of the above code scatter around in my model classes. I would like to refactor the transaction handling part out of the models and stay DRY.

I thought I could using closure like the following:

// in parent CI_Model class 
class MY_Model extends CI_Model {
  public function txn_wrap($closure) {
    $this->db->trans_start();
    $closure();
    $this->db->trans_complete();
    if ( $this->db->trans_status() == FALSE ) {
        $this->handle_db_error();
    }
  }

// in child model class

 class Blog_model extends MY_Model {
   protected $_table = 'app_blog';

   public function get($id) {
     $instance = $this;
     $closure = function() use($instance, $id) { 
        // do some db updates
        $instance->db->update($instance->_table, array('title' => 'bla'), array('id' => $id));
     };
     $this->txn_wrap($closure);
   }

That doesn’t work and gives me "PHP Fatal error: Using $this when not in object context". So I guess using of $this usage is not supported in 5.3.

Now failing of using closure, What else can I do?

UPDATE: now I am getting Undefined property: App_Blog::$_table where App_About is the controller which calls the get() function in Blog_model. I have tried function() use($instance, , $instance->_table, $id) but php complains about the syntax.. Now this closure thing doesn’t appears give me as much benefits as I thought..

thanks!

Answer 1

The closure is not a method of your child model class, so you cannot access the instance. You will need to provide it to the closure:

$instance = $this;
$table = $this->_table;
$update_db_closure = function() use ($instance, $table) {
    // do some db updates
    $instance->db->update($table, ...);
    $instance->db->update($table, ...);
};

The $this->_table property is protected, thus you won’t be able to access it inside the closure, so you need to pass a copy of it.