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reflection

Run this example with no other examples loaded at the same time.

This folder contains an example that shows how to implement a reflective class-based system. There are three main classes:

[111, 98, 106, 101, 99, 116]

root of the inheritance graph

[99, 108, 97, 115, 115]

default metaclass for all instantiable classes

[97, 98, 115, 116, 114, 97, 99, 116, 95, 99, 108, 97, 115, 115]

default metaclass for all abstract classes

Each class inherit all the methods form the other two classes and from itself (without any inheritance loops of course ;-).

You can find more sophisticated versions of these classes in the roots example. If you are not familiar with the concept of metaclass used in this example, see the metaclasses example first.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the example:

logtalk_load(reflection(loader)).

Print the (public and protected) interface of each class:

object::print, abstract_class::print, class::print.

<!-- Object: object

interface: new/1 delete/1 instances/1 metaclass/0 abstract_class/0 strict_instance/0 print/0

Object: abstract_class

interface: new/1 delete/1 instances/1 metaclass/0 abstract_class/0 strict_instance/0 print/0

Object: class

interface: new/1 delete/1 instances/1 metaclass/0 abstract_class/0 strict_instance/0 print/0

true. -->

The object Class is the metaclass of all classes:

class::instances(Instances), class::metaclass.

<!-- Instances = [class,abstract_class,object]. -->

Create an abstract class, check it and print its interface:

abstract_class::new(ac), ac::abstract_class, ac::print.

<!-- Object: ac

interface: metaclass/0 abstract_class/0 strict_instance/0 print/0

true. -->

Try to create an instance of the abstract class:

catch(ac::new(i), Error, true).

<!-- Error = error(existence_error(predicate_declaration,new(i)),ac::new(i),user). -->

Create a new instantiable class and print its interface:

class::new(c), c::print.

<!-- Object: c

interface: new/1 delete/1 instances/1 metaclass/0 abstract_class/0 strict_instance/0 print/0

true. -->

Create an instance of the new class:

c::new(i), c::instances(Instances).

<!-- Instances = [i]. -->

Because c does not declare any predicates, its instances have no interface:

\+ i::current_predicate(_).

<!-- true. -->

Create an instance of object, root of the inheritance graph, and print its interface:

object::new(j), j::print.

<!-- Object: j

interface: strict_instance/0 print/0

true. -->

Delete the dynamic objects that we created:

c::delete(i), class::delete(c), abstract_class::delete(ac), object::delete(j).

<!-- true. -->