Re: Template multiple inheritance
dec4106 wrote:
That's what I thought but either I don't understand it (obviously...)
or the compiler doesn't support it. Here's a more complete example,
compiled with VS 2008:
Actually, this example is a very different one, apart from the fact that it
still uses templates which Pete suggested to remove. Removing that would
make things clearer and this should be your job even before posting here.
Anyway...
template <typename T, int port>
struct PortProvider : public Provider<T>
{
virtual ~PortProvider() {}
virtual T getValue() const
{
return getPortValue();
}
virtual T getPortValue() const = 0;
};
class BS :
public PortProvider<MyData, 1>,
public PortProvider<MyData, 2>
The important change to your previous example is here: The first template
parameter and thus the return type for getPortValue() is the same here,
while it was different before.
virtual MyData PortProvider<MyData, 1>::getPortValue() const
{}
virtual MyData PortProvider<MyData, 2>::getPortValue() const
{}
I guess here you are struggling with how to override the two virtual
functions required by the two baseclasses. Bad news: You can't. Since both
are the same returntype, both are overrided by the same function.
Roughly, the reason is how name lookup works. First, it looks up the name,
going to baseclasses when not found. Then, if multiple overloads exist in
the used class, it tries to disambiguate them using parameters (overload
resolution). Your two functions have the same name and the same parameters.
You can't overload a function with the same parameters.
BTW: Concerning your initial question, you can explicitly specify who's
function to call by prefixing the function name with "classname::". However,
this only applies to calling a function, not to declaring it as above. This
is probably also what Pete referred to when he advised you to drop the
template stuff in order to gain understanding.
int _tmain(int argc, _TCHAR* argv[])
This is not portable, read the FAQ.
BS * bs1(new BS);
Why are you using new here?
Uli
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