[C++11] - building properties with my own code

[joaquim]

i have seen several codes for do properties and some need more work to build them, so i came up with my own code:

#include <iostream>
#include <functional>

using namespace std;

template <typename T>
class property
{
private:
    T PropertyValue;
    std::function<void(void)> getf;
    std::function<void(T a)> setf;
public:
    property()
    {
        //nothing
    };

    property(T value)
    {
        PropertyValue=value;
    };

    property(std::function<void(void)> GetFunction,std::function<T(void)> SetFunction)
    {
        setf=SetFunction;
        getf=GetFunction;
    }

    property& operator=(T value)
    {
        if(setf==NULL)
            PropertyValue=value;
        else
            setf(value);
        return *this;
    }

    T& operator=(property value)
    {
        if(getf==NULL)
            return PropertyValue;
        else
            return getf();
    }

    friend ostream& operator<<(ostream& os, const property& dt)
    {
        os << dt.PropertyValue;
        return os;
    }

    friend istream& operator>>(istream &input,property &dt)
    {
        input >> dt.PropertyValue;
        return input;
    }
};

class test
{
public:

    test()
    {
        //nothing
    }
    property<string> Name;
    property<int> Age;

};

test a;

int main()
{
    a.Name="joaquim "  "Miguel";
    a.Age=10+15;
    cout << a.Age << endl;
    cout << "What is your age?\n";
    cin >> a.Age;
    cout << "your age is: " << a.Age << endl;
    return 0;
}

these code works fine and no errors, but when i choose the get and set functions, i get several errors

#include <iostream>
#include <functional>

using namespace std;

template <typename T>
class property
{
private:
    T PropertyValue;
    std::function<void(void)> getf;
    std::function<void(T a)> setf;
public:
    property()
    {
        //nothing
    };

    property(T value)
    {
        PropertyValue=value;
    };

    property(std::function<void(void)> GetFunction,std::function<T(void)> SetFunction)
    {
        setf=SetFunction;
        getf=GetFunction;
    }

    property& operator=(T value)
    {
        if(setf==NULL)
            PropertyValue=value;
        else
            setf(value);
        return *this;
    }

    T& operator=(property value)
    {
        if(getf==NULL)
            return PropertyValue;
        else
            return getf();
    }

    friend ostream& operator<<(ostream& os, const property& dt)
    {
        os << dt.PropertyValue;
        return os;
    }

    friend istream& operator>>(istream &input,property &dt)
    {
        input >> dt.PropertyValue;
        return input;
    }
};

class test
{
private:
    int age;
    int getage()
    {
        return age;
    }
    void setage(int value)
    {
        age=value;
    }
public:

    test()
    {
        //nothing
    }
    property<string> Name;
    property<int> Age(&getage,&setage);

};

test a;

int main()
{
    a.Name="joaquim "  "Miguel";
    a.Age=10+15;
    cout << a.Age << endl;
    cout << "what is your age?\n";
    cin >> a.Age;
    cout << "your age is: " << a.Age << endl;
    return 0;
}

now i get several errors like:
- error: expected identifier before '&' token;
- error: invalid use of member function (did you forget the '()' ?);
- error: no match for 'operator<<' (operand types are 'std:stream {aka std::basic_ostream<char>}' and '<unresolved overloaded function type>')|
(and more warnings and errors)
(i belive that i know why these last error is when i overload the << and >> operators)
can anyone advice me, please?