深度剖析C++对象池自动回收技术实现

#pragma once
#include <memory>
#include <vector>
#include <functional>
template <class T>
class SimpleObjectPool
{
public:
  using DeleterType = std::function<void(T*)>;
  void add(std::unique_ptr<T> t)
  {
    pool_.push_back(std::move(t));
  }
  std::unique_ptr<T, DeleterType> get()
  {
    if (pool_.empty())
    {
      throw std::logic_error("no more object");
    }
    //every time add custom deleter for default unique_ptr
    std::unique_ptr<T, DeleterType> ptr(pool_.back().release(), [this](T* t)
    {
      pool_.push_back(std::unique_ptr<T>(t));
    });
    pool_.pop_back();
    return std::move(ptr);
  }
  bool empty() const
  {
    return pool_.empty();
  }
  size_t size() const
  {
    return pool_.size();
  }
private:
  std::vector<std::unique_ptr<T>> pool_;
};
//test code
void test_object_pool()
{
  SimpleObjectPool<A> p;
  p.add(std::unique_ptr<A>(new A()));
  p.add(std::unique_ptr<A>(new A()));
  {
    auto t = p.get();
    p.get();
  }
  {
    p.get();
    p.get();
  }
  std::cout << p.size() << std::endl;
｝

std::shared_ptr<T> get()
{
if (pool_.empty())
{
throw std::logic_error("no more object");
}
std::shared_ptr<T> ptr = pool_.back();
auto p = std::shared_ptr<T>(new T(std::move(*ptr.get())), [this](T* t)
{
pool_.push_back(std::shared_ptr<T>(t));
});
//std::unique_ptr<T, DeleterType> ptr(pool_.back().release(), [this](T* t)
//{
// pool_.push_back(std::unique_ptr<T>(t));
//});
pool_.pop_back();
return p;
}