Data mapper and zend framework

Question

I am implementing the Data Mapper design pattern in my Zend Framework web application, and everything goes well, I am really enjoying working with the data mapper in Zend and not applying only the Row Gateway pattern, but I am having a problem regarding my architecture. I am not sure how to reference and work with foreign key constraints in a OOP fashion with my data mapper. So I am having my Model class, my DbTable class and my Mapper class. Should I put all the foreign keys relations in my DbTable class and in this way I can retrieve in my mapper using findDependentRowset() function, or a better approach would be to instantiate the dependent class in my mapper. What is the best OOP practice in mapping foreign keys using the Data Mapper pattern?

If you have lots of Impedance Mismatch, consider using an ORM, like Doctrine2. — Gordon, Oct 01 '11 at 11:17
I already started the project with the data mapper implementation, only problem I am having is handling foreign key mapping if either to instantiate objects or to let the DbTable be aware of the database schema — Mythriel, Oct 01 '11 at 11:43
My implementation is something like this: Model - same as what you said, but without any functions, only setters and getter for accessing Model properties DbTable - no functions here, only subclassing Zend_Db_Table_Abstract and providing the id and name for the table DataMapper - does the meat - here I have all the functions and i retrieve the DbTable class and set the properties with the Model class I want my system to be as loose coupled as it can, so the problem is my foreign key relations in my application — Mythriel, Oct 01 '11 at 11:49

score 4 · Answer 1 · answered Oct 01 '11 at 11:25

I'd go for the DataMapper as the other two shoudln't be aware of the ID per se althought it's always necessary for the relationship callers.

Model
- Property accessors and private property data holders
- Functions regarding correct usage of model
- Relatioship callers (calls relationship fetches in the DbTable to get parents or children rows)or returns cached data

DbTable
- Provides all static functions used to query data and instanciate the related Models such as :getById, getByName, getByComplexSearch, etc
- Provides all static relationship loaders such as: getParents, getChildrens and any other version you need

DataMapper
- Does the real meat and provides the getObjects method which accepts either a query part or a full query and loads the data into the ModelObjects and reads it back into a update, insert, delete query when needed
- Datamapper should be in charge of checking for relationship faults when inserting, updating or deleting using transactions if in InnoDB.

Does that make any sense?

score 2 · Answer 2 · edited May 23 '17 at 12:30

I used to have findDependentRowset on my systems. But not anymore! It's a waste of resources in most cases. Table joins should be on your SQL statement.

See my answer here: Hand made queries vs findDependentRowset

~~I'm still far away from use Doctrine or Propel (I've never needed it). Maybe some day.~~ (Now using Doctrine 2. So... I suggest you the same now)

OLD ANSWER

After a couple of years working with Zend Framework, I come across with the following architecture:

1) I have an abstract mapper which all my mappers extends: Zf_Model_DbTable_Mapper

2) I have an abstract model (domain object) too, similar to the Row Data Gateway, with the exception that it is not a gateway. It's a generic domain object: Zf_Model

3) When populating object graphs (SQL joins) one mapper delegates to the other mappers that are responsible for the given object.

Example

This method is from the abstract mapper:

    public function getById($id) 
    {


        $tableGateway = $this->getTable();

        $row = $tableGateway->fetchRow('id =' . (int) $id);

        if (!$row) 
            retur null;

        $row = $row->toArray();

        $objectName = $this->getDomainObjectName();
        $object = new $objectName($row['id']);
        $object->populate($row);

        return $object;    
    }

Data mapper and zend framework

2 Answers2

OLD ANSWER