在运行时从指向基类的指针获取对象的类型

我正在使用一个类库，其中所有类都直接或间接派生自基类Base并有一个名字。该库提供了按名称搜索对象的功能，该功能将返回Base*.

有没有办法在不检查所有可能性的情况下找到返回对象的类型dynamic_cast就像我在下面的例子中所做的那样？如果可能的话，我想避免这种情况，因为派生类具有模板参数，这带来了很多可能性。

如果我至少能够找出班级类型（T1 or T2，在下面的示例中）而不知道模板类型，即。做类似的事情dynamic_cast<T1<i_dont_care>*>.

#include <iostream>

using namespace std;

class Base {
public:
    virtual ~Base() {}
};

template <typename T> class T1 : public Base {};
template <typename T> class T2 : public Base {};

Base *find_by_name() {
    return new T2<int>();
}

int main() {
    Base *b = find_by_name();

    if (T1<int> *p = dynamic_cast<T1<int>*>(b)) {
        cout << "T1<int>" << endl;
        // do something meaningful with p
    } else if (T1<double> *p = dynamic_cast<T1<double>*>(b))
        cout << "T1<double>" << endl;
    else if (T2<int> *p = dynamic_cast<T2<int>*>(b))
        cout << "T2<int>" << endl;
    else if (T2<double> *p = dynamic_cast<T2<double>*>(b))
        cout << "T2<double>" << endl;
    else
        cout << "unknown" << endl;

    delete b;

    return 0;
}

请注意，上面的示例是简化的，即。每一个if我会做一些有意义的事情p.

我确实意识到这从一开始就是糟糕的设计，但是我坚持使用这个库，而且我也没有办法改变它的实现。

有类似的东西typeid http://en.cppreference.com/w/cpp/language/typeid http://en.cppreference.com/w/cpp/language/typeid，应用于多态表达式将在运行时评估其类型表示。

以下维基示例：https://en.wikipedia.org/wiki/Run-time_type_information#dynamic_cast https://en.wikipedia.org/wiki/Run-time_type_information#dynamic_cast

#include <iostream> 
#include <typeinfo>    // for 'typeid'

class Person {
public:
   virtual ~Person() {}
};

class Employee : public Person {
};

int main() 
{
    Person person;
    Employee employee;
    Person* ptr = &employee;
    Person& ref = employee;
    // The string returned by typeid::name is implementation-defined

    // Person (statically known at compile-time)
    std::cout << typeid(person).name() << std::endl;   

    // Employee (statically known at compile-time)
    std::cout << typeid(employee).name() << std::endl; 

    // Person* (statically known at compile-time)
    std::cout << typeid(ptr).name() << std::endl;      

    /* Employee (looked up dynamically at run-time
     * because it is the dereference of a
     * pointer to a polymorphic class) */
    std::cout << typeid(*ptr).name() << std::endl;     

    // Employee (references can also be polymorphic)        
    std::cout << typeid(ref).name() << std::endl;      
}