Problem with function selection in templates

[Pär Buschka]

Hi there.

I have some template functions that operate on different types of object. If
the object has a certain memberfunction I want to call that function, and if
not, I want to call a global function that operates on that object.

Some pseudocode to show what I mean:

template<class T> void Function(T& MyObject)
{
if exist MyObject.Process() then MyObject.Process();
else GlobalProcess(MyObject);
}

is there a good way to do this without having to write a lot of overloaded
functions for one of the cases?

Thanks in advance
Pär Buschka

 

[Victor Bazarov]

I have some template functions that operate on different types of
object. If the object has a certain memberfunction I want to call
that function, and if not, I want to call a global function that
operates on that object.
Some pseudocode to show what I mean:

template<class T> void Function(T& MyObject)
{
if exist MyObject.Process() then MyObject.Process();
else GlobalProcess(MyObject);
}

is there a good way to do this without having to write a lot of
overloaded functions for one of the cases?

template<class T, bool usemember> struct ObjectProcessor;

template<class T> struct ObjectProcessor<T, true> {
void operator()(T& MyObject) {
MyObject.Process();
}
};

template<class T> struct ObjectProcessor<T, false> {
void operator()(T& MyObject) {
GlobalProcess(MyObject);
}
};

template<class T> void Function(T& MyObject)
{
ObjectProcessor<T, has_member< ??? > >()(MyObject);
}

Look up a suitable implementation of "has_member" on the Web.

V

 

[Pär Buschka]

Thank you very much for the help, it seems to work perfect.

A suitable has_member function can for instance be found at:
http://www.tech-archive.net/Archive/DotNet/microsoft.public.dotnet.languages.vc/2004-10/0007.html

/Pär