Re: Ada Interfaces and the Liskov Substitution Principle

[Maciej Sobczak <see.my.homepage@gmail.com>]

On 25 Maj, 10:21, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:

> > Interesting. In most of the cases, the factory function creates the
> > object of whatever type *it* decides (based on its parameters or some
> > other input values) and initializes the class-wide type accordingly.
>
> Not necessarily. In one case, I generate nodes of a graph. The nodes can be
> of different types regarding their persistence. For example, there are
> nodes resident in the database and nodes resident in the memory etc. Now,
> when creating a new node a factory moves along two axes: the standard
> root/branch/leaf hierarchy and persistence stuff. For the latter the
> factory receives an already existing node, to create "a new node like
> this." This is not copying. Ideally it should double dispatching along both
> axes. I have implemented it as:
>
>    New_Node := Create (Get_Factory (Some_Existing_Node), ...);

Above, it is the factory function that is "parameterized" on the left-
hand type - this is still much different from assignment_statement
(wow!) between two class-wide types. I'm still for banning it.

> > There is a very simple rule of thumb for checking whether any given OO
> > pattern makes sense - try to stick it to the classical geometry
> > example.
> > If it falls off, beware. :-)
>
> You certainly mean the circle-ellipse LSP controversy... (:-))

Ontological relationships have nothing to do with behavioral
substitutability. There is no controversy there, only confusion. ;-)

--
Maciej Sobczak
http://www.msobczak.com/