c ++ realize Any class

This blog reference to achieve any type of c ++ Any kind of , a little change. Original blog is to use a generic placeholder variable Holder object to hold the data, rather than the template class Any, Any class constructor is a template function to different types of data stored in the Holder. Any class implements this operation type erasure mainly used here is void*a pointer, that is simply a combination of any of the data memory address and interpretation mode, void*the pointer can point to any type of data stored pointer (i.e., memory address), the remaining reuse a string class variable to hold its type (i.e. how the data interpretation).
Using this embodiment setDatafunctions Any object class on a specific set of data using a getDatafunction to parse the data stored Any, both of which are generic functions:

class Any
{
public:
	Any() :pData(NULL), type("null") {}
	template<class ValueType>
	Any(const ValueType& value) { setData(value); }
	template<class ValueType>
	void setData(const ValueType& value) { pData = (void*)(&value); type = typeid(value).name(); }
	template<> void setData<Any>(const Any& value) { if (this != &value) { this->pData = value.pData; this->type = value.type; } }
	template<class ValueType>
	bool getData(ValueType& dst) { if (!isCompatible(dst))return false; dst = *(ValueType*)(pData); return true; }
	template<class ValueType>
	bool isCompatible(const ValueType& value) { return (string)(typeid(value).name()) == string(this->type); }
	void* getAddress() { return pData; }
	const char* getType() { return type; }
	bool isNull() { return pData == NULL; }
	template<class ValueType>
	Any& operator=(const ValueType& value) { this->setData(value); return *this; }
	template<class ValueType>
	operator ValueType() { return *(ValueType*)(pData); }
	template<class ValueType>
	void display() { string t = (string)type; cout << "地址为:" << this << "的Any对象指向地址为:" << this->pData << "的" << this->type << "类型的数据:" << *(ValueType*)(pData) << endl; }
private:
	void* pData;
	const char* type;
};

Wherein constructors Any(const ValueType& value)and =operator overloading simply called setDataonly provides a convenient use; comprising operator ValueType()also a convenient way of providing the Any type to the other type of conversion; Any of the display()functions just for testing. The test is as follows:

class Test
{
public:
	int h = 4;
	void display() { cout << "Test对象地址:" << this << ",h=" << h << endl; }
};

int main()
{
	Any any, any1;
	int a = 7, a1;
	float b = 4.1, b1;
	double c = 0.315, c1; 
	string s1 = "Hello", s2;
	Test t, t1;
	t.h = 5;
	t1.h = 15;
	any = a;
	any.display<int>();
	a1 = any;
	cout << "a1=" << a1 << endl;
	any = b;
	any.display<float>();
	b1 = any;
	cout << "b1=" << b1 << endl;
	any = c;
	any.display<double>();
	c1 = any;
	cout << "c1=" << c1 << endl;
	any = s1;
	any.display<string>();
	any.getData(s2);
	//s2 = any;
	cout << "s2=" << s2 << endl;
	t.display();
	any = t;
	t1.display();
	t1 = any;
	t1.display();
	any1 = any;
	system("pause");
    return 0;
}

Any class can be assigned can be seen as int, float, doubleetc. basic types as well string, and custom Testtype, a little fly in the ointment is that if you save Any object stringtype can not directly through the =assignment operator to stringthe type of variable, there will be “operatr=”不明确errors. I currently do not know what causes this. The following are the results:

the proposed use is:

• Any object to the assignment: direct use of =operators, such asany=b
• Any object assigned to the other variables: want to call isCompatiblefunction to determine whether the same type, and then use the getDatafunction; for some basic types of int, float, doublecan be used directly =operator to assign to other types Any object, but the =operator does not check the type of embodiment.

The method of the present embodiment is more similar to this blog achieve Any class .

Any additional boost class is defined in the library, you can use ready-made wheels.