Extending Database Drivers

Category:Help | Category:Help::TipsAndTricks | Category:Help::Databases

Much complaints about not being able to extend the CI database class. In the docs it says this can't be done, but here is a simple solution that fits it all! [b]Don't believe it?, well read on..[/b]

[h4]The solution comes in 3 simple steps:[/h4]

[b]1)[/b] Extend your loader class by creating the file MY_Loader.php. Put it into your libraries directory in the application path: [code]<?php

class MY_Loader extends CI_Loader {

}

?> [/code]

[b]2)[/b] Add the following function to your MY_Loader class: [code] /** * Database Loader * * @access public * @param string the DB credentials * @param bool whether to return the DB object * @param bool whether to enable active record (this allows us to override the config setting) * @return object */ function database($params = '', $return = FALSE, $active_record = FALSE) { // Do we even need to load the database class? if (class_exists('CI_DB') AND $return == FALSE AND $active_record == FALSE) { return FALSE; }

        require_once(BASEPATH.'database/DB'.EXT);

        // Load the DB class
        $db =& DB($params, $active_record);

        $my_driver = config_item('subclass_prefix').'DB_'.$db->dbdriver.'_driver';
        $my_driver_file = APPPATH.'libraries/'.$my_driver.EXT;

        if (file_exists($my_driver_file))
        {
            require_once($my_driver_file);
            $db =& new $my_driver(get_object_vars($db));
        }

        if ($return === TRUE)
        {
            return $db;
        }
        // Grab the super object
        $CI =& get_instance();

        // Initialize the db variable.  Needed to prevent
        // reference errors with some configurations
        $CI->db = '';
        $CI->db = $db;
        // Assign the DB object to any existing models
        $this->_ci_assign_to_models();
}[/code]

[b]3)[/b] Create your Database driver extension class, that you name MY_DB_mysql_driver.php (or substitute the mysql part for whatever driver you use - do that also for the classnames in the code below!). Put this file also in your applications libraries directory: [code]<?php

class MY_DB_mysql_driver extends CI_DB_mysql_driver {

function __construct($params){ parent::__construct($params); log_message('debug', 'Extended DB driver class instantiated!'); }

function get_first($table){ return $this->limit(1)->get($table); }

} ?>[/code]

[b]Congrats, now you can use your own db functions![/b] Eg. get_first($table), the sample function from above, now fetches the first entry from your table:[code]$this->db->get_first('sometable');[/code] [h4]Other Example Functions[/h4] (put them also in your Extended DB driver class) [code] /** * nests like, where statements * order in select clause is WHERE - LIKE * so WHERE a=0 OR ((WHERE b=0 AND c LIKE '%me%') OR m LIKE '%us') AND f LIKE '%nobody% * is possible */ function nest($kind, $start, $end, $kind2=false){ $kind = 'ar_'.$kind; $this->{$kind}[$start-1] = preg_replace('/(^AND )|(^OR )|^/', "$1$2(", $this->{$kind}[$start-1]); if($kind2){ $kind = 'ar_'.$kind2; } $this->{$kind}[$end-1] .= ')'; return $this; }

  /**
  * a limit function that takes an array or an integer,
  * so you only need one argument ever
  */
  function ulimit($limit){
   if($limit){
        if(is_array($limit)){
            $this->limit($limit[0], $limit[1]);
        }else{
            $this->limit($limit);
        }
    }
    return $this;
  }[/code]

[h4]Extending DB_Cache functionality[/h4] You can use the same trick to extend the functionality of the DB_Cache library. Copy the DB_Cache.php file from the system/libraries directory to your APPPATH/libraries directory. Then add this to your MY_Loader library: [code] /** * Database Loader extension, to load our version of the caching engine * * @access public * @param string the DB credentials * @param bool whether to return the DB object * @param bool whether to enable active record (this allows us to override the config setting) * @return object */ function database($params = '', $return = FALSE, $active_record = FALSE) { // load our version of the CI_DB_Cache class. The database library checks // if this class is already loaded before instantiating it. Loading it now // makes sure our version is used when a controller enables query caching if ( ! class_exists('CI_DB_Cache')) { @include(APPPATH.'libraries/DB_Cache'.EXT); }

    // call the parent method to retain the CI functionality
    parent::database($params, $return, $active_record);
}[/code]