In C++ how to convert a string to class object?

Question

For example i have a class named "WaterScene", in the.xml i have saved as string "WaterScene" when i read the.xml i have to convert that string to class. One approach is just string comparison

if( string == "WaterScene")
return new WaterScene;

Is there any generic way to do this to avoid string comparison? Like in objective C(dynamic language) we can get the class using string...

Class classObject =[[NSBundle mainBundle] classNamed:string];

Answer 1

If all of the objects you would be returning are derived from a common base class, you could use a std::map<std::string,BaseClass *> . The comparisons ultimately in there somewhere, but it keeps things better organized.

Answer 2

No, you can't do it with standard C++. C++ has no notion of reflection . Sorry:)

Answer 3

I think you could probably use an implementation that leverages the Abstract Factory Pattern . Here is a pretty good article on a Boost centric implementation .

Answer 4

No. At some level, a string comparison must be done in your code. C++ doesn't have any mechanism for that kind of dynamic programming.

Answer 5

No. But to elegantly get around this limitation I would enumerate all possible classes and create an array of corresponding class names:

enum ECLASSTYPE
{
  CT_WATER_SCENE,
  CT_SOME_OTHER,
  CT__MAX,
};

static const string g_classNames[CT__MAX] =
{
  "WaterScene", // CT_WATER_SCENE
  "SomeOther", // CT_SOME_OTHER
};

When parsing xml, decode the string name to enum and pass it to the factory method:

switch (classType)
{
  case CT_WATER_SCENE:
  {
    result = new WaterScene();
    break;
  }
  ...
}

Answer 6

I have used Generic Class factory to solve the issue... First i am registering class and storing it in a map before main().