.. This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2024 Paulo Moura <pmoura@logtalk.org> SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

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.. rst-class:: align-right

built-in predicate

.. index:: pair: define_events/5; Built-in predicate .. _predicates_define_events_5:

define_events/5

Description

::

define_events(Event, Object, Message, Sender, Monitor)

Defines a new set of events. The two types of events are represented by the atoms before and after. When the predicate is called with the first argument unbound, both types of events are defined. The object Monitor must define the event handler methods required by the Event argument.

Modes and number of proofs

::

define_events(@term, @term, @term, @term, +object_identifier) - one

Errors

| Event is neither a variable nor a valid event identifier: | type_error(event, Event) | Object is neither a variable nor a valid object identifier: | type_error(object_identifier, Object) | Message is neither a variable nor a callable term: | type_error(callable, Message) | Sender is neither a variable nor a valid object identifier: | type_error(object_identifier, Sender) | Monitor is a variable: | instantiation_error | Monitor is neither a variable nor a valid object identifier: | type_error(object_identifier, Monitor) | Monitor does not define the required before/3 method: | existence_error(procedure, before/3) | Monitor does not define the required after/3 method: | existence_error(procedure, after/3)

Examples

::

% define "debugger" as a monitor for member/2 messages % sent to the "list" object: | ?- define_events(_, list, member(_, _), _ , debugger).

.. seealso::

:ref:predicates_abolish_events_5, :ref:predicates_current_event_5, :ref:methods_before_3, :ref:methods_after_3