Re: [fw-mvc] Understanding 'Service Layer' and 'Domain Model'

The service layer is helpfulc in shielding your controller from nasty logic involving one or more domain objects. For example, if there is some complicated logic involved in creating a new event (let's say there's a difference between whether an administrator is creating it or an "organization" is creating it, that would go in the service layer. Or perhaps if you need to do some ACL checks while looking retrieving some resources, that would go in the service layer.

On Tue, Sep 1, 2009 at 7:48 AM, Colin J <colin.johnson@johnguest.co.uk> wrote:

Wondered if anyone might be able to help.

I have been reading Matthew Weier O'Phinney's Zend Framework slides from the 2009 Dutch PHP Conference (thank you Matthew for making the slides available, they have been extremely useful).

One aspect I am trying to understand is determining what to put in the service layer and what to put in the domain model. I don't fully understand the difference. I just wondered whether anyone may be able to give a small example/explanation.

An example of my confusion is as follows. If I have a controller which requests a list of users from the service layer. Sometimes I want all users, and sometimes current users (status of 1), would I have 2 methods each (e.g. fetchUsers, fetchCurrentUsers) in the service layer, the domain model AND the data mapper code?

Or would I have a fetchAll method in the Data Mapper and call from the domain model:

function fetchUsers() {     $dataMapper->fetchAll(array()); }  function fetchCurrentUsers() {     $dataMapper->fetchAll(array('status' => 1)); } 

or have a fetchAll in the domain Model and call from the service layer:

function fetchUsers() {     $domainModel->fetchAll(array()); }  function fetchCurrentUsers() {     $domainModel->fetchAll(array('status' => 1)); } 

My problem actually stemmed from having a query which joined 2 tables containing a 'status' column which meant I needed to specify somewhere that my status was for the user table. So, I would need:

function fetchBannedUsers() {     $domainModel->fetchAll(array('u.status' => 1)); } 

But should the service layer 'know' about the database structure?

Colin

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