Question

in C++, i have the class Base as a interface class and 2 inheritance class: Base1 and Base2 from Base class like this:

class Base{
    public:
        virtual void printSomething() = 0;
    // Some bla bla code...
};

class Base1 : public Base{
    public:
        Base1();
        void printSomething(); 
};


class Base2 : public Base{
    public:
        Base2();
        void printSomething(); 
};

In normal way, in my main.cpp, i have to include following code:

Base *b;
string base_name = "Base1"; // or "Base2" 
if(base_name.compare("Base1") == 0){
     b = new Base1();
}else{
     b = new Base2();
}

So, i want to using Base *b = base_name() instead of if()else() block above. In c++, is this possible, anh how? thanks!

Answer 1

Unlike Java, C++ does not offer native support of the reflection concept. You can write a simple function to construct the specific Base instance. This is called a Factory:

Base* create_base_instance(string name) {
  if (name == "Base1")
    return new Base1();
  if (name == "Base2")
    return new Base2();
  throw runtime_error("unknown class name");
}

Base *b;
string base_name = "Base1"; // or "Base2" 
b = create_base_instance(base_name);