我应该如何重构我的代码以删除不必要的单例? [英] How should I refactor my code to remove unnecessary singletons?
问题描述
当我第一次开始看到反单音的评论时，我感到很困惑.我在最近的一些项目中使用了单例模式，并且效果很好.事实上，我已经使用了很多次.
I was confused when I first started to see anti-singleton commentary. I have used the singleton pattern in some recent projects, and it was working out beautifully. So much so, in fact, that I have used it many, many times.
现在，遇到一些问题后，阅读这个 SO问题，尤其是这篇博客文章，我了解我为网站带来的邪恶世界.
Now, after running into some problems, reading this SO question, and especially this blog post, I understand the evil that I have brought into the world.
所以:我该如何从现有代码中删除单例?
So: How do I go about removing singletons from existing code?
例如:
在零售商店管理程序中，我使用了MVC模式.我的模型对象描述了商店，用户界面是视图，并且我有一组充当两者之间联络人的控制器.伟大的.除了将Store变成一个单例(因为该应用程序一次只能管理一个商店)，而且我还将我的大多数Controller类也变成了Singleton(一个mainWindow，一个menuBar，一个productEditor ...).现在，我的大多数Controller类都可以访问其他单例，如下所示:
For example:
In a retail store management program, I used the MVC pattern. My Model objects describe the store, the user interface is the View, and I have a set of Controllers that act as liason between the two. Great. Except that I made the Store into a singleton (since the application only ever manages one store at a time), and I also made most of my Controller classes into singletons (one mainWindow, one menuBar, one productEditor...). Now, most of my Controller classes get access the other singletons like this:
Store managedStore = Store::getInstance();
managedStore.doSomething();
managedStore.doSomethingElse();
//etc.
我应该改为:
- 为每个对象创建一个实例，并将引用传递给需要访问它们的每个对象?
- 使用全局变量?
- 还有别的吗?
- Create one instance of each object and pass references to every object that needs access to them?
- Use globals?
- Something else?
Globals would still be bad, but at least they wouldn't be pretending.
我看到#1很快导致构造函数调用急剧膨胀:
I see #1 quickly leading to horribly inflated constructor calls:
someVar = SomeControllerClass(managedStore, menuBar, editor, sasquatch, ...)
还有其他人经历过吗?在公共变量而不是全局变量或单例变量的情况下，给许多单独的类赋予访问权限的OO方法是什么?
Has anyone else been through this yet? What is the OO way to give many individual classes acces to a common variable without it being a global or a singleton?
推荐答案
依赖注入是您的朋友.
在优秀的Google测试博客上查看这些帖子:
- 信箱是病理骗子(但您如果您要问这个问题，可能已经知道了)
- 关于依赖注入的讨论
- 编写可测试代码的指南
- Singletons are pathologic liars (but you probably already understand this if you are asking this question)
- A talk on Dependency Injection
- Guide to Writing Testable Code
希望有人为C ++世界做了一个DI框架/容器? Google似乎发布了 C ++测试框架和
Hopefully someone has made a DI framework/container for the C++ world? Looks like Google has released a C++ Testing Framework and a C++ Mocking Framework, which might help you out.
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