Dear All,

 I'm looking for an easy way to handle object references with Z3 with
 schema and widgets.

 The UML diagram is rather simple for example:
+--------------+                +-------------+
| <<entity>>   |           unit | <<entity>>  |
|    Unit      | <------------- |   Item      |
+--------------+                +-------------+
| +unit:string |                | +code:string|
+--------------+                | +name:string|
                                | +cost:int   |
More complex classes are to come of course. The Unit objects are
modifiable by the user, they cannot be hard-coded.

I would write the interfaces like this:

class IUnit(Interface):
    """Unit, measurement unit"""
    unit = TextLine(title=u"Unit",description=u"Unit",required = True)

class IItem(Interface):
    """Item, that can be stored in the warehouse"""

    code = TextLine(title=u"Code",description=u"code",required = True)
    name = TextLine(title=u"Name",description=u"name",required = True)
    cost = Int(title=u"Cost",description=u"Cost",required = False)

    unit = Object(title=u"Unit",description=u"the item is measured with this",
                  schema=IUnit, required = True)

I'm not 100% sure, that Object() is the right one for that. For the
current situation maybe it's OK, for many-to-many and complicated
references I think schoolbell.relationship should be better for that.

class IUnitContainer(IContainer):
    """Unit Container"""

class ISubitemContainer(IContainer):
    """Subitem Container"""

Now a widget would be nice, which allows to select a unit from the
UnitContainer with a combobox or something.
The current ObjectWidget seems like a kind of in-place input of the properties
of the schema. I'm not sure that I got it 100%.

Any hint, sample, pointing out a product to check is appreciated.

Best regards,
 Groszer Adam

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