C++：组织程序子系统的正确方法是什么？
假设您有一个大型应用程序项目，代码被分为一系列子系统，这些子系统作为从 CBaseSubsystem 派生的类实现。
我的第一个问题已经出现：
- 将子系统组织为类（从基类派生）是一个好主意吗？
然后，您就有了子系统类。现在，您需要在某处创建它们的实例。但在哪里呢？
将每个子系统实例存储在全局变量中是个好主意吗，例如：
extern CEventSystem* g_EventSystem;实例应该在哪里实际创建？所有这些都在一个类似 main() 的函数中？
或者完全避免全局变量并将实例组织在
CSubsystemManager类或类似类中更好？使用单例类是合适的方法吗？
Imagine you have a large application project, the code is split into a range of subsystems implemented as classes derived from CBaseSubsystem.
Here already comes my first question:
- Is it a good idea to organize subsystems as classes [derived from a base class]?
Then, you have your subsystem classes. Now, you will need create have instances of them somewhere. But where?
Is it a good idea to have every subsystem instance stored in a global variable, for example:
extern CEventSystem* g_EventSystem;Where should the instances be actually created? All together in a main()-like function?
Or is it better to avoid global variables entirely and organize the instances in a
CSubsystemManagerclass or the like?Would using singleton classes be an appropriate approach?
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与这个非常相似。我会避免使用 Singleton，因为这里绝对没有必要，并且会带来关于许多其他问题。
在类似 main 的例程中创建实例。如果某些东西需要系统，请通过某种方式提供对其的访问，无论是直接传递给该东西的参数还是提供对这些系统的访问的容器（IE：CSubSystemManager）。您可能不需要编写 CSubSystemManager。
避免全局状态，这是它被耻辱的原因。
Very similar to this. I'd avoid Singleton, because it is absolutely unnecessary here and brings about many other issues.
Create the instances in a main-like routine. If something needs a system, provide access to it through some means, be it a parameter passed directly to that something or a container that provides access to these systems (IE: CSubSystemManager). You likely don't need to go so far as to write CSubSystemManager.
Avoid global state, there's a reason it has a stigma.
如果您需要一种方法来访问每个子系统的实例，我会避免使用“extern”，而是使用一个单例来访问 CSubsystemManager 的实例。管理器本身可以负责实例化和管理子系统对象。
If you need a way to access an instance of each subsystem, I would avoid using "extern" and instead go with a singleton that gives you access to an instance of CSubsystemManager. The manager itself can take care of instantiating and managing your subsystem objects.
如果您想谈论理论而不是提供具体问题，请考虑根据 Factory 和 Singleton 以及可能的 子系统中的策略，可以对一系列不同的对象类型实现类似的操作。
主子系统 Factory 本身就是一个单例，我希望其目的是显而易见的。使用延迟计算仅允许根据需要加载所需的子系统对象。您可能需要考虑为每个子系统提供引用计数机制，以便在不再需要时将其删除。一些子系统本身可能是单例和/或也可以实现策略模式来为一系列类类型提供特定服务。
这个服务可能是例如验证、渲染、序列化等。
以这种方式构建应用程序是否是一个“好主意”的价值判断不是我能说的。我宁愿让古老的智慧来阐述这一点。
If you want to talk theory rather than provide a concrete question then consider designing in terms of a combination of Factory and Singleton with the possibility of Strategy in subsystems which may implement a similar operation for a range of different object types.
The main subsystem Factory is itself a singleton whose purpose is I hope obvious. Use lazy evaluation to allow only required subsystem objects to be loaded as needed. You may want to consider providing each subsystem with a reference counting mechanism which will allow them to be dropped when no longer needed. Some subsystems may themselves be singletons and/or may also implement Strategy pattern to provide a particular service for a range of class types.
This service may be for example validation, rendering, serialisation etc.
The value judgement of whether it is a "good idea" to build your application in this way is not for me to say. I would rather let older wisdom speak to that.
我的解决方案将创建单例注册表、抽象工厂和工厂的组合。
My solution would create a combo of a singleton Registry, AbstractFactory and Factory.