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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2023 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

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Design pattern: State

Description: "Allow an object to alter its behavior when its internal state changes. The object will appear to change its class."

This pattern can be used with both classes and prototypes.

We use prototypes in this sample implementation. The context object uses a dynamic predicate to hold the current concrete state object identifier with a public predicate to set it. The concrete state objects perform the context-switching after handling a forwarded client request.