.. 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

directive

.. index:: pair: initialization/1; Directive .. _directives_initialization_1:

initialization/1

Description

::

initialization(Goal)

When used within an object, this directive defines a goal to be called after the object has been successfully loaded into memory. When used at a global level within a source file, this directive defines a goal to be called after the source file is successfully compiled and loaded into memory.

The loading context can be accessed from this directive by calling the :ref:predicates_logtalk_load_context_2 predicate. Note that the usable loading context keys depends on the directive scope (file or object).

Multiple initialization directives can be used in a source file or in an object. Their goals will be called in the same order as the directives at loading time.

.. note::

Arbitrary goals cannot be used as directives in source files. Any goal that should be automatically called when a source file is loaded must be wrapped using this directive.

Categories and protocols cannot contain initialization/1 directives as the initialization goals would lack a complete :term:`execution context <predicate execution context>` that is only available for objects.

Although technically a global initialization/1 directive in a source file is a Prolog directive, calls to Logtalk built-in predicates from it are usually compiled to improve portability, improve performance, and provide better support for embedded applications.

.. warning::

Some backend Prolog compilers declare the atom initialization as an operator for a lighter syntax. But this makes the code non-portable and is therefore a practice best avoided.

Template and modes

::

initialization(@callable)

Examples

::

% call the init/0 predicate after loading the % source file containing the directive

:- initialization(init).

::

% print a debug message after loading a % source file defining an object

:- object(log).

:- initialization(start_date).

start_date :-
    os::date_time(Year, Month, Day, _, _, _, _),
    logtalk::print_message(debug, my_app, 'Starting date: ~d-~d-~d~n'+[Year,Month,Day]).

:- end_object.

.. seealso::

:ref:predicates_logtalk_load_context_2