>I have found out that you can work around this: if you define a
>property in the parent object and issue ...
>
>this.Property= createObject('BehaviourClass')

Of course. This is what I was saying: CreateObject() instead of AddObject().

>It has all the advantages of the addobject method, without the
>disadvantage of the parent class having to be a container.

Exactly.

>> 1. You will have the following relations between objects (triangle of
>> relations):
>> Container->Behavior
>> Container->AnObject
>> AnObject->Behavior
>
>This, to be honest, I do not understand.

It means:
The container ownes the Behavior
The container ownes the AnObject
The AnObject ownes the Behavior

When you have a situation like this, VFP 3.0 will fail to destroy these objects. because:
If the AnObject is to be destroyed first: it can't do it because AnObject points to Behavior, which is not destroyed yet.
If the Behavior is to be destroyed first: it can't do it because AnObject points to Behavior and AnObject is not destroyed yet.
I've heard that VFP 5.0 works better, but I had no time to test it.

>> This means that you must write additional code to be able to destroy these
>> obects correctly.
>
>You do this in the base classes no?

Yes, you can do it, but it's an useless overwork.

>
>> 2. The container will be loaded with some (usually) non-visual objects.
>
>So ?

It means that each time the container will scan its collection of objects (Refresh, etc), it will process some extra objects. And I don't see any use of it. It will only slow down some actions.

>> 3. It reduces the generality <snip>
>
>The price to pay to use composition i.o. inheritance ...

Yes. But if you don't need composition, why use it? :)

>Yes. But this problem would be solved (and others probably created) if
>we had multiple inheritance, i.e. that a class could inherit from
>multiple classes (i.o.w., multiple superclasses).

This is true. But multiple inheritance has its big pitfalls as well.

>> >This way all the base classes can share methods _and_ properties ... or
>> >am I missing something?
>>
>
>Well all the properties that are owned by the behaviour class are
>accessible by the objects of classes that own this behaviour class. Or
>is something else meant by 'sharing properties'?

Yes. The problem is you can't use these properties directly (e.g. Object.Property). And you can't chain/hook properties directly.

The real power of these Behavior classes/objects is that you can chain/hook them.

Have a nice weekend,
Vlad