DataMapper ORM v1.8.0

[eluser]WanWizard[/eluser]
I have to guess what your models look like, but from the information given, you have created a many-to-many relationship between customers and notes. You create such a relation by using a junction or relationship table (customers_notes), which contains the primary keys of both tables in the relationship (which in Datamapper must be called 'id').

The line

Code:

$cus->save($not->all);

saves the relationship between the currently loaded customer (in the $cus object) and all retrieved notes (all objects in the $not->all array). It does that by inserting records in the relationship table, with $cus->id, and all id values of the retrieved notes.

Nothing magical, standard database design, and how you whould have to implement it by hand if you use active record.

When you now use

Code:

$cus->note->get();

Datamapper will generate a join on the relationship table and the notes table, selecting the records in the relationship table whose customer_id equals $cus->id.

If you want to know what happens behind the scenes, use check_last_query() after a Datamapper command, and analyse the SQL to see what exactly happens.