c++ - 如何在C++中编写通用对象池

Question

我想编写一个通用对象池类，并且对象池应该是单例的，很容易在任何地方访问该对象池。

template <class T>
class Pool
{
    T* _freeObjs;
 public:
    Pool<T>& getInstance()
    {
        static Pool<T> instance;
        return instance;
    }
    
    T* acquire() { ... }
    
    void release(T* obj) { ... }
    
 private:
    Pool()
    {
        _freeObjs = (T*)malloc(sizeof(T) * 100);
    }
};

class Foo
{
    int i;
public:
    void* operator new(size_t size) 
    { 
        void * p = Pool<Foo>::getInstance().acquire();
        return p; 
    } 
  
    void operator delete(void * p) 
    {  
        Pool<Foo>::getInstance().release(p);
    } 
};

int main()
{
    {
        Foo* f = new Foo();
        delete f;
    }
    
    return 0;
}

但是编译器显示以下错误消息，
错误:无法在没有对象的情况下调用成员函数“Pool＆Pool::getInstance()[with T = Foo]”
无效* p = Pool::getInstance()。acquire();
更新:谢谢PaulMcKenzie
在将静态方法添加到getInstance()函数之后，该代码即可正常工作。
现在，如果我的以下代码有任何错误，我将重载运算符new / delete移至基类。

class PooledObject
{
public:
    void* operator new(size_t size) 
    { 
        void * p = Pool<PooledObject>::getInstance().acquire();
        return p; 
    } 
  
    void operator delete(void * p) 
    { 
        Pool<PooledObject>::getInstance().release((PooledObject*)p);
    } 
};

class Foo : public PooledObject
{
    int i;
public:
};

Answer 1

您的Pool<T>& getInstance()不是static。如果要在不创建对象的情况下访问static，则它必须是getInstance函数:

static Pool<T>& getInstance()
{
    static Pool<T> instance;
    return instance;
}