unique_ptr看不到派生类的自定义构造函数

Question

class A{
    string m_name;
    int m_num;
public:
    A(string name="", int number=0) : m_name(name), m_num(number)
    { cout << "ctorA " << m_name << endl; }

    virtual ~A(){ cout << "dtorA " << m_name << endl; }

    string getName(){ return m_name; }
    void setName(const string name){ m_name = name; }
    int getNumber(){ return m_num; }
};

class B : public A{
    string m_s;
public:
    B(string name="", int number=0, string s="")
        : A(name, number){ m_s = s; }

    string getS(){ return m_s; }

};


auto upB = unique_ptr<B>("B", 2, "B");   //ERROR HERE


error: no matching function for call to 'std::unique_ptr<B>::unique_ptr(const char [2], int, const char [2])'

我不明白为什么它没有看到B构造函数.一切似乎都很好.使用默认构造函数:

auto upB = unique_ptr<B>();

我做错了什么或派生类有什么特殊问题？

Answer 1

auto upB = std::make_unique<B>("B", 2, "B");

要么

auto upB = std::unique_ptr<B>(new B("B", 2, "B"));

下面std::unique_ptr<B>是空的,就像是nullptr.

auto upB = unique_ptr<B>();