When you write :
We can see a syntax error. It should be :
(if $this->user is set)

you can use this syntax for dynamic var names, for example

Its the function that is called relative to layout being generated.
It provides data for a specific layout / view

function _buildQuery_default() - is the query for your tables default view
function _buildQuery() - defines the FK dropdown / combo box data (i think? from memory)

If you had two layouts for the same table

1) userdetails
2) usercontact

if your default table was userdetails...
you would have

function _buildQuery()
function _buildQuery_default()
function _buildQuery_usercontact()

if your default layout was usercontact
you would have
function _buildQuery()
function _buildQuery_userdetails()
function _buildQuery_default()

As for
function addWhere($where_clause)
it puts the item at the end of the statement
its useful if you need to define a query that returns a list of items containing specific data such as town, gender, postcode

for instance

. addWhere($address_town->id=4)
. buildQuery_WhereAuthor()

Would Give...
WHERE $user->id = 43 AND $address_town->id = 4
And the record would be returned if user #43 lived in town #4

If you understand MySql well enough and echo, copy and dump the query into your Mysql Interface it becomes a lot easier to understand whats happening

@admin
OK what you suggest ($this->user->id) is also working... so I 've choosen this way.

I was also wondering the purpose of some methods in the models (as they have no header comments)
active() and
activeAll()

can you briefly explain.
Thks