[Zope] editing zclass instance properties

[Olivier Laurent]

Hello,

I've created a zclass to manage a list of tasks to be done with some properties called todo_title, todo_priority, todo_expiry,...
The propertysheet is called 'todo_info', the product 'ToDoProduct' and the zclass 'todo'

Each instance is created in a folder called 'todos' with names like 'a982706331', 'a456812195',...

I put the instance id in a variable called 'todo_id'

I'm trying to change zclass instance properties. I followed the Zope Developer's Guide :
<dtml-call "a982706331.manage_changeProperties({'todo_title':'Do this'})">
but nothing changes (no error messages).
I tried a lot of different things like :

<dtml-with "todo.createInObjectManager(REQUEST['todo_id'],REQUEST)">
<dtml-call expr="propertysheets.todo_info.manage_editProperties({'todo_title':'Do that'})">
</dtml-with>

or

<dtml-with todo_id>
<dtml-call "manage_editProperties({'todo_title':'Do this'})">
</dtml-with>

or

<dtml-with todo_id>
<dtml-call "manage_changeProperties({'todo_title':'Do that'})">
</dtml-with>

Could someone help me fix the problem ?

Also : what's the difference between 'manage_editProperties' and 'manage_changeProperties' ?

Thanks,

Olivier Laurent.