built-in method

# `before/3`

## Description

    before(Object, Message, Sender)

User-defined method for handling before events. This method is declared in the monitoring built-in protocol as a public predicate and automatically called by the runtime for messages sent using the (::)/2 control construct from within objects compiled with the events flag set to `allow`.

Note that you can make this predicate scope protected or private by using, respectively, protected or private implementation of the `monitoring` protocol.

## Modes and number of proofs

    before(?object_identifier, ?callable, ?object_identifier) - zero_or_more

## Errors

(none)

## Examples

    :- object(...,
        implements(monitoring),
        ...).

        % write a log message when a message is sent:
        before(Object, Message, Sender) :-
            writeq(Object), write('::'), writeq(Message),
            write(' from '), writeq(Sender), nl.

See also

after/3, abolish_events/5, current_event/5, define_events/5