构建可扩展C++类库的框架

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"A Framework for Building Extensible C++ Class Libraries - 1993-计算机科学" 这篇1996年发表的文章探讨了一个用于构建可扩展C++类库的框架,由Arindam Banerji、Dinesh C. Kulkarni和David L. Cohn共同撰写,他们当时在University of Notre Dame的分布式计算研究实验室工作。文章是1993年的技术报告93-12的成果,讨论了可扩展性在软件设计和重用性提升中的重要性。 在C++编程中,类库是软件开发的基础,它们提供了预定义的功能集合,可以被其他程序或类使用。然而,随着需求的变化和技术的进步,类库需要不断更新和扩展以适应新的功能和性能要求。该框架提出了一种方法,使得类库不仅能够在最初设计时满足需求,而且还能在未来轻松地添加新功能或修改现有功能,从而实现其可扩展性。 文章的核心内容可能涵盖了以下几个关键知识点: 1. **面向对象设计**:C++作为面向对象的编程语言,通过封装、继承和多态等特性支持可扩展性。作者可能会详细介绍如何利用这些特性来构建可扩展的类库。 2. **接口设计**:良好的接口设计是实现类库可扩展性的关键。接口应该是清晰、简洁且独立于具体实现的,以便于添加新的实现或修改现有实现而不影响其他部分。 3. **模板和泛型编程**:C++的模板机制允许创建泛型代码,这可以在不修改原有类库的情况下提供对不同数据类型的通用支持,增强了类库的灵活性和可扩展性。 4. **插件架构**:通过设计插件系统,类库可以加载和卸载额外的模块,允许用户根据需要添加功能,而不必更改核心代码。 5. **设计模式**:文章可能会讨论一些设计模式,如工厂模式、观察者模式等,这些模式是实现类库可扩展性和模块化的重要工具。 6. **版本控制与兼容性**:在扩展类库时,需要考虑向后兼容性,确保旧版本的代码仍能在新版本的库上运行,同时避免引入破坏性的改变。 7. **测试与文档**:为了保证类库的可扩展性,完善的测试套件和清晰的文档是必不可少的,它们帮助开发者理解类库的工作方式并进行安全的修改。 8. **案例分析**:作者可能通过具体的例子或案例展示了如何使用这个框架来构建和扩展实际的C++类库,以证明其有效性和实用性。 这篇文章深入研究了如何在C++中构建能够随着时间推移持续演进的类库,这对于理解和实践软件工程的可维护性和可扩展性原则具有重要意义。

3)A digital clock consists of a screen to display the time and a dial for setting in turn the year, month, day, hour and minute. Twisting the dial to the left reduces by one the value being changed but twisting it to the right increases it by one. Pushing the dial alters which value is being adjusted. At first, it is the year but after the dial is pushed once, it is the month, then after the dial is pushed again, it is the day and so on. Imagine the clock is represented by a class with attributes year, month, day etc. The following is what the code for a method rotateDialLeft() might look like. public void rotateDialLeft() { if (mode == YEAR_MODE) { year--; } else if (mode == MONTH_MODE) { month--; } else if (mode == DAY_MODE) { day--; } else if (mode == HOUR_MODE) { hour--; } else if (mode == MINUTE_MODE) { minute--; } } The code for rotateDialRight() is similar. Apply the Open-Closed Principle to explain why the above code is unsatisfactory from the design viewpoint, considering the possibility of future change to the code, giving an example of such a change. 5)Give the code required for the classes introduced in question 3), focusing on the code for a method selectState() which changes the value that is being adjusted from years to months. Make it clear in which classes the code is to be found. Assume the existence of other methods that are needed such as getMonthSetUpState(). 8)Suppose that in a multiplayer role-playing game, a class Client has a dependency to an interface Fighter with public methods attack(), defend() and escape(). The game designer now wishes for Client to use a class Wizard with three different but equivalent public methods castDestructionSpell(), shield() and portal(). Explain how it is possible to do this using an appropriate design pattern.

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