A String & Number Compatible ID Class in Native C++

I'm a game programmer, plenty of IDs maybe typed as unsigned int are very common in my game code; and in some context, I'd like to convert a numeric ID into string or parse it back from a string; such conversions often go with ID operations together. I hated conversions everywhere, so I decided to make an ID tool class as below:

template<typename T>
class AutoId {
public:
	AutoId() {
		mNum = T(0);
		mStr = "";
		mNumDirty = false;
		mStrDirty = true;
	}
	AutoId(T n) {
		mNum = n;
		mNumDirty = false;
		mStrDirty = true;
	}
	AutoId(const std::string &s) {
		mStr = s;
		mStrDirty = false;
		mNumDirty = true;
	}
	AutoId(const AutoId<T> &other) {
		mNum = other.mNum;
		mStr = other.mStr;
		mNumDirty = other.mNumDirty;
		mStrDirty = other.mStrDirty;
	}
	~AutoId() {
	}
	AutoId<T> &operator = (const AutoId<T> &other) {
		mNum = other.mNum;
		mStr = other.mStr;
		mNumDirty = other.mNumDirty;
		mStrDirty = other.mStrDirty;
		return this;
	}
	AutoId<T> &operator = (T n) { // numeric setter
		mNum = n;
		mNumDirty = false;
		mStrDirty = true;
		return *this;
	}
	AutoId<T> &operator = (const std::string &s) { // string setter
		mStr = s;
		mStrDirty = false;
		mNumDirty = true;
		return *this;
	}
	operator T(void) { // numeric getter
		if(mNumDirty) {
			assert(!mStrDirty);
			std::istringstream ss(mStr);
			ss >> mNum;
			mNumDirty = false;
		}
		return mNum;
	}
	operator std::string(void) { // string getter
		if(mStrDirty) {
			assert(!mNumDirty);
			std::ostringstream ss;
			ss << mNum;
			mStr = ss.str();
			mStrDirty = false;
		}
		return mStr;
	}
private:
	T mNum;
	std::string mStr;
	bool mNumDirty;
	bool mStrDirty;
};

The recipe is those operator overloadings. The guard variables mNumDirty and mStrDirty keep that conversions will occur when it is really necessary. To use this code, you may just get or set either type string or numbers like:

AutoId<int> id1(5);
AutoId<float> id2("3.14");
AutoId<unsigned int> id3; id3 = 400;
AutoId<double> id4; id4 = "5423.234236";

int nid1 = id1;
std::string sid1 = id1;

float nid2 = id2;
std::string sid2 = id2;

unsigned int nid3 = id3;
std::string sid3 = id3;

double nid4 = id4;
std::string sid4 = id4;

Hope this helps if you need it. Any suggestions are appreciated.