On the surface, it appears that Zend\Db\TableGateway corresponds to
Zend_Db_Table, Zend\Db\ResultSet to
Zend_Db_TableRowset, and Zend\Db\RowGateway to Zend_Db_Table_Row. If so, should
I use the ZF2 classes the same way I did
their counterparts in ZF1, or has the whole paradigm shifted?
This is more or less correct. Now, they are not completely coupled,
they all can be used independent of one another. One of the stronger
use cases for this independence is that in many cases, you don't
necessarily want a RowGateway object as a result from a TableGateway object.
But in the ZF2 User's Guide, the example code appears to have Album\Model\Album
taking the place of the
Zend_Db_Table_Row in ZF1. If that's correct, where does Zend\Db\RowGateway fit
in?
In that particular example, the "Table" objects are implementing the
Table Module pattern:
http://martinfowler.com/eaaCatalog/tableModule.html
and are composing TableGateway objects to do their work. The
distinction here is a that the Table Module API deviates from that of
purely TableGateway (very database-ish) and moves closer to the "models"
API.
Also in the User's Guide, the Album\Model\AlbumTable seems to be a very thin
Mapper. Wouldn't a concrete TableGateway
have worked just as well in this simple app? If so, would we still use the
AlbumTableGateway factory in
Module->getServiceConfig()?
There's no right or wrong answer here. Every modeling pattern comes
with pro's and con's. A concrete TableGateway would work as well,
instead of passing it off as a "Mapper".
And wouldn't the default ArrayObject prototype work just as well as
Album\Model\Album? What's the advantage of that class?
I'm probably making this harder than it needs to be, but it seems that while
the Guide does a fairly good job of explain
WHAT is going on, it just doesn't explain the WHY.
Help me Obi-Wan-ZendObi. You're my only help.
ArrayObject would work, but you dont get the same kind of data type
validation you would get by using a concrete-type "Entity", like Album.
For example, in the AlbumTable->save() method, you'll note that it
only accepts an Album. If all the various table modules used
ArrayObject, then you'd have to do additional checking to ensure the
right table is getting the right kind of ArrayObject.
You might also want to have a look at Rob Allens approach, which this
tutorial was lightly based off of:
https://github.com/akrabat/zf2-tutorial/
Hope that helps getting you started.
-ralph
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