c : Is it possible to find class type by string?-CodePudding

Let's say I have some class:

class A {};
class B {};
...

I want to implement a function as:

auto cs[2] = {A, B};
for(int i=0; i<2; i  )
{
    auto ob = new cs[i];
}

Is it possible?

If it is impossible, is the following code possible?

auto cs[2] = {"A", "B"};
for(int i=0; i<2; i  )
{
    auto ob = new stringToClass(cs[i]);
}

What should stringToClass be?

Any suggestion is appreciated~~~

Update

Sorry for this unclearing question. The reason why I ask this question is because that I need to new many class. Just like:

auto a = new A;
auto b = new B;
...

Thus, I want to new these class by for-loop.

CodePudding user response：

It is not clear what you are actually trying to do, but it is not possible to have a loop where each iteration resolves auto to different types. But if your only purpose is to call constructors of several types where the types should be provided as an "array-like structure", you may use template metaprogramming (e.g. you may want to warm up the cache). For example:

template<typename C>
auto createClass() {
    return std::make_unique<C>();
}

template<typename T>
struct Creator {
    static void createClasses() { }
};

template<typename C, typename... Cs>
struct Creator<tuple<C, Cs...>> {
    static void createClasses() {
        createClass<C>();
        Creator<tuple<Cs...>>::createClasses();
    }
};

The createClass() template function creates an instance of the class, and Creator::createClasses creates many classes based on the type of the tuple:

struct A {
    A() { std::cout << "A::A()" << std::endl; }
};

struct B {
    B() { std::cout << "B::B()" << std::endl; }
};

using Classes = std::tuple<A, B>;

int main()
{
    Creator<Classes>::createClasses();
    return 0;
}

the output is:

A::A()
B::B()

As you may noticed, the createClass() function returns an unique_ptr, and the created classes are destroyed immediately. That is up to you to figure out what to do with that.

CodePudding user response：

I want to new these class by for-loop It's Not Possible in c

template <class T>
void AllocateMemoryInHeap () {
   T obj = new T ();
   return obj;
}

// Usage : 
std::vector <type_t> types; // Err : it's not possible to store types in array
for (int i = 0 ; i < 100 ; i    ) 
    auto anyVar = AllocateMemoryInHeap <types[i]> ();