从流中读取数组

我们需要重载运算符以从模板类的流中读取。模板类 Set 有一个字段 - 另一个模板类 Point 的元素数组：

class Set
{
public:

    Set()
    {
        _ptr = nullptr;
        _capacity = 0;
        _size = 0;
    }

    Set(int capacity)
    {
        _ptr = new classType[capacity];
        _capacity = capacity;
        _size = 0;
    }
    template<class classType>
    friend ostream& operator << (ostream& os, const Set<classType>& set);

    template <class classType>
    friend istream& operator >> (istream &stream, Set<classType>& set);
}

class Point
{
public:

    Point()
    {
        _x = 0;
        _y = 0;
        _z = 0;
    }

    Point(T x, T y, T z)
    {
        _x = x;
        _y = y;
        _z = z;
    }
    template<typename T>
    friend ostream& operator << (ostream& os, const Point<T>& p);

    template<typename T>
    friend istream& operator >> (istream &stream, Point<T>& p);
}

实现本身：

    template <class classType>
istream &operator >> (istream &stream, Set<classType>& set)
{
    cout << "Enter capacity: ";
    stream >> set._capacity;
    cout << "Enter size: ";
    stream >> set._size;

    cout << "Enter elements: ";
    for (int i = 0; i < set._size; ++i)
        stream >> set._ptr[i];
    return stream;
}

template <typename T>
istream &operator >> (istream &stream, Point<T>& p)
{
    stream >> p._x >> p._y >> p._z;
    return stream;
}

读取容量 b 大小并开始从 _ptr (_ptr[0]) 读取第一个元素后从 gtests 崩溃

测试截图：

告诉我该怎么做？