具有依赖项的C ++策略设计 [英] C++ Policy design with dependencies

问题描述

这是对此问题的跟踪.

基本上，我想要一个存储对象的容器，以后再对它们进行处理.我想将对对象(ActionPolicy)执行的操作和存储(StoragePolicy)都放入策略类.最后，该类上应该有两个函数:

Basically I want a container that stores objects and later does something with them. I want to put both, the action performed on the objects (ActionPolicy), and the storage (StoragePolicy), into policy classes. At the end, there should be two functions on the class:

• addObject()，其签名取决于ActionPolicy，即应在此处定义此功能.
• execute()，它将遍历StoragePolicy存储的所有对象，并对所有对象执行ActionPolicy::evaluate(obj).

• addObject() with a signature depending on ActionPolicy, i.e. this function should be defined in there.
• execute(), which goes over all of the objects stored by StoragePolicy and executes ActionPolicy::evaluate(obj) on all of them.

在(部分伪)代码中(标记为Here的位置在该设计中不起作用):

In (partially pseudo-)code (the places marked with Here are the ones that don't work in this design):

struct ActionPolicy {
  // Signature is dependant on this policy
  void addObject(T obj, /* ... */) {
    // Do something with the object
    StoragePolicy::store(obj); // <--- Here
  }

  void eval(T obj) {
    // Do something with the object
  }
};

struct StoragePolicySingle {
  T obj;

  void store(T obj) {
    this->obj = obj;
  }

  void execute() {
    ActionPolicy::execute(obj); // <--- Here
  }
};


struct StoragePolicyMulti {
  std::vector<T> vec;

  void store(T obj) {
    vec.push_back(obj´);
  }

  void execute() {
    for (obj in vec) {
      ActionPolicy::execute(obj); // <--- Here
    }
  }
};

template <class A, class B> MyClass : public A, public B {
  // ...
};

所有这些都对性能至关重要，因此我不能只使用带有一个条目的向量来代替StoragePolicySingle.

All of this is performance-critical, so I can't just use a vector with one entry instead of StoragePolicySingle.

您将如何解决?我缺少任何模式吗?

How would you solve this? Any pattern I'm missing?

推荐答案

为什么ActionPolicy需要了解StoragePolicy?

为什么ActionPolicy中添加了对象?

如果将ActionPolicy传递给StoragePolicy作为execute的参数，然后在单个项目或集合上调用eval，这是否为您解决呢?

If you pass the ActionPolicy to the StoragePolicy as an argument to execute, then call eval on either the single item or the collection, does this not solve it for you?

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