DataMapper 1.6.0

[eluser]OverZealous[/eluser]
I've been working on what I believe is a critical addition to DataMapper: a where_related method. It was actually really simple, although I have not yet thoroughly tested it.

If you already have a DataMapper subclass, you can add the following code to it:

Code:

/**
* Get
*
* Overridden to reset the _added_related array
*
*/
function get ($limit = NULL, $offset = NULL)
{
    $ret = parent::get($limit, $offset);
    // clear the _added_related array
    $this->_added_related = array();
    return $ret;
}


// --------------------------------------------------------------------

/**
* Where Related
*
* Limits a query to a related object's field.
*
* @access    public
* @param    object
* @param    string
* @param    string
* @return    this
*/
function where_related($object, $field = NULL, $value = NULL, $or = FALSE)
{
    if (is_null($object))
    {
        show_error('where_related requires a valid related Object');
    }
    if (is_null($object->id) && is_null($field))
    {
        show_error('where_related requires a field or object id');
    }
    
    if ($field == NULL)
    {
        $field = 'id';
        $value = $object->id;
    }
    $this->_add_related($object, $field, $value, $or);
    
    return $this;
}

// --------------------------------------------------------------------

/**
* Or Where Related
*
* Limits a query to a related object's field.
*
* @access    public
* @param    object
* @param    string
* @param    string
* @return    this
*/
function or_where_related($object, $field = NULL, $value = NULL) {
    return $this->where_related($object, $field, $value, TRUE);
}


// --------------------------------------------------------------------

// used to keep track of related items
var $_added_related = array();

/**
* Related
*
* Finds all related records of this objects current record.
*
* @access    private
* @param    string
* @param    integer
* @return    void
*/
function _add_related($object, $field, $value, $or)
{

    // Prepare model
    $model = ucfirst(strtolower($object->model));
    //$object = new $model;

    $this->model = strtolower($this->model);

    // Determine relationship table name
    $relationship_table = $this->_get_relationship_table($object->prefix, $object->table, $object->model);

    // Retrieve related records
    if (empty($this->db->ar_select))
    {
        $this->db->select($this->table . '.*');
    }

    // Check if self referencing
    if ($this->table == $object->table)
    {
        if ( ! in_array($model, $this->_added_related) )
        {
            // can only perform where on id's for self-referencing
            if($field != 'id') {
                show_error('Cannot perform where_related queries on self-referencing tables unless field is id');
            }
            $this->db->join($relationship_table, $object->table . '.id = ' . $this->model . '_id', 'left');
            $this->db->where($relationship_table . '.' . $object->model . '_id = ' . $value);
            array_push($this->_added_related, $model);
        }
    }
    else
    {
        // only add the table if it wasn't already joined
        if ( ! in_array($model, $this->_added_related) )
        {
            $this->db->join($relationship_table, $this->table . '.id = ' . $this->model . '_id', 'left');
            $this->db->join($object->table, $object->table . '.id = ' . $object->model . '_id', 'left');
            array_push($this->_added_related, $model);
        }
        if($or)
        {
            $this->db->or_where($object->table . '.' . $field, $value);
        }
        else
        {
            $this->db->where($object->table . '.' . $field, $value);
        }
    }

    $this->model = ucfirst($this->model);
}

Usage:
If you want to filter a query based on the values of a related object, you call where_related before calling the get.
Example:

Code:

// get all admins
$u = new User();
$access = new Access();
$u->where_related($access, 'level', 'admin');
$u->get();

You can also use it to filter on a specific item easily:

Code:

$u = new User();
$access = new Access();
$access->where('level', 'admin')->get();
$u->where_related($access);
$u->get();

Finally, you can use standard the where format:

Code:

$u = new User();
$access = new Access();
$u->where_related($access, 'level >=', 2);
$u->get();

Limitations
There is only one real limitation. A self-referencing table can ONLY query by ID. I could not think of an easy way around this.

You can have multiple where_related or or_where_related statements.

Let me know if there are any errors, or if you find transcription errors. I made some changes while typing this, so I might have made a typo.