Re: [Qemu-devel] [PATCH qom-next 1/7] qdev: Push state up to Object

[Anthony Liguori]

On 06/10/2012 10:49 AM, Paolo Bonzini wrote:
> Il 08/06/2012 03:19, Anthony Liguori ha scritto:
> > > +typedef enum ObjectState {
> > > +    OBJECT_STATE_INITIALIZED = 1,
> > > +    OBJECT_STATE_REALIZED,
> > > +} ObjectState;
> >
> > I think using a bool would be better since it reduces the temptation to
> > add additional states.
>
> In fact someone already discussed having a third state for block
> devices... :)

This is *exactly* why bool is better.  Because too many people will be tempted 
to add stuff that doesn't belong in Object.

A classic problem with OO design is bloating base classes--especially when you 
have one common base class.

Everything in Object must be relevant to all subclasses, not just some.  Having 
an OBJECT_STATE_OPENED only makes sense for BlockDevices.  Therefore the concept 
of opened should live in the BlockDevice parent class.

Regards,

Anthony Liguori

> Paolo