Transparent Class Wrapper

[mike]

Ok,
IO want to write a class to wrap around another class, to print to the
screen when the vale is changed. So far I have:
template<class T>
class Tracer
{
T data;
public:

Tracer()
{
cout << "New Tracer:" << T() <<"\n";
data = T();
}

Tracer(const T& t)
{
cout << "New Tracer:" << t<<"\n";
data = t;
}

T& operator=(const T& t)
{
cout << "TracerChanged: " << t<<"\n";
data = t;
}


};
allowing me to write:
Tracer<int> a;
Tracer<int> b = 6;
b = 12;
a=4;

but i can't go the other way around:
int e = a; //Error

Now i seem to remeber an explicit operator, and I googled for it this
morning but no luck??
Any thoughts would be apprieciated!

Mike

[Gernot Frisch]

"mike" <sl***********@hotmail.com> schrieb im Newsbeitrag
news:11**********************@f14g2000cwb.googlegr oups.com...

Ok,
IO want to write a class to wrap around another class, to print to
the
screen when the vale is changed. So far I have:
template<class T>
class Tracer
{
T data;
public:

Tracer()
{
cout << "New Tracer:" << T() <<"\n";
data = T();
}

Tracer(const T& t)
{
cout << "New Tracer:" << t<<"\n";
data = t;
}

T& operator=(const T& t)
{
cout << "TracerChanged: " << t<<"\n";
data = t;
}


};
allowing me to write:
Tracer<int> a;
Tracer<int> b = 6;
b = 12;
a=4;

but i can't go the other way around:
int e = a; //Error

Now i seem to remeber an explicit operator, and I googled for it
this
morning but no luck??
Any thoughts would be apprieciated!

operator T() {return data;}

HTH,
-Gernot

[Mike Wahler]

"mike" <sl***********@hotmail.com> wrote in message
news:11**********************@f14g2000cwb.googlegr oups.com...

Ok,
IO want to write a class to wrap around another class, to print to the
screen when the vale is changed. So far I have:


#include <iostream>
using std::cout;
template<class T>
class Tracer
{
T data;
public:

Tracer()
{
cout << "New Tracer:" << T() <<"\n";
data = T();
}
Tracer() : data(T())
{
cout << "New Tracer:" << data << '\n';
}

Tracer(const T& t)
{
cout << "New Tracer:" << t<<"\n";
data = t;
}
Tracer(const T& t) : data(t)
{
cout << "New Tracer:" << t << '\n';
}
T& operator=(const T& t)
{
cout << "TracerChanged: " << t<<"\n";
data = t;
return data = t;
}

operator T() const
{
return data;
}

};
allowing me to write:
int main()
{
Tracer<int> a;
Tracer<int> b = 6;
b = 12;
a=4;

but i can't go the other way around:
int e = a; //Error
return 0;
}

Now i seem to remeber an explicit operator, and I googled for it this
morning but no luck??
Any thoughts would be apprieciated!

What you were looking for is 'conversion operator'.

-Mike

[mike]

Thanks, thats the ticket!
Mike

[Gernot Frisch]

"mike" <sl***********@hotmail.com> schrieb im Newsbeitrag
news:11**********************@g49g2000cwa.googlegr oups.com...

Thanks, thats the ticket!
Mike

Ooops! Forgot the "const" at the end:
operator T() const {return data;}

otherwise you might get stange errors some day...