Creating nested relationships with an ORM and minimizing queries

First of all, I'm sorry to break this to you , but CodeIgniter's DataMapper is actually a variation of ActiveRecord pattern.

If you care, you compare the real DataMapper pattern with its counterpart - ActiveRecord. In short - difference is in fact that in DM pattern you Domain Object is unaware of type ( and even the existence ) of storage. It is used in manner like $mapper->store( $user );.

"Favor object composition over class inheritance." © GoF

That said..

If i read the examples right then it should work like this:( i am assuming that relationships between 'entities' are already established )

class Project extends DataMapper{   // --- the rest of your stuff    public function get_all_points()   {      $points = array();      $slides = $this->slide->get()->all;      foreach ( $slides as $slide )      {         $shapes = $slide->shape->get()->all;         foreach ( $shapes as $shape )         {            $points = array_merge( $point = $shape->point->get();         }      }      return $points;   }}

Then you can use something like

$project = new Project;$all_points = $project->where( 'id' , 1 )->get_all_points();foreach ( $all_points as $point ){   $point->x = 0;   $point->save();}

This should gather all th points that are related to project with ID 1, and set the X value to 0 and store each in the database .. not that any sane person would do it.

I am not using any sort of ORM, that's why i really hope i got this wrong, because this looks to me like an abomination.

I'm not sure how Datamapper does it but I have a custom GenericObject model for Codeigniter that does ORM like this:

class Article extends GenericObject{    public $relationships = array ( "has_many" => array ("comments"), "has_one" => array ("users") );}class Comments extends GenericObject{    public $relationships = array ( "belongs_to" => array ("articles", "users"), "has_one" => array ("users") );}class Users extends GenericObject{    public $relationships = array ( "has_many" => array ("comments", "articles") );}

If I want to get everything from a User then I can just do something like:

$User = new User( $some_user_id );$User->boot_relations("all");foreach ($User->Comments as $Comment){    echo $Comment->title."<br />";    echo $Comment->body."<br />";    echo "written by ".$User->username;}

So it can be fairly elegant (or at least I like to think so).

With most relational data, I typically lazy-load objects at they are needed. I'm not a PHP developer, but here's what I would do in pseudo-code.

class Projects {    var slides = null;    function getSlides() {        if(slides == null) {            slides = getSlidesForProject(this.id);        }        return slides;    }}class Slides {    var shapes = null;    function getShapes() {        if(shapes == null) {            shapes = getShapesForSlide(this.id);        }        return slides;    }}class Shapes {    //... same as Projects.getSlides and Slides.getShapes}

Unfortunately, this causes multiple calls to the database if you needed to get all Points for a Project.

With any MVC solution, I recommend going with a light Controller and a heavy Model to make code reuse and testing easier.