Hello Karsten,
Karsten Schwenk wrote:
> I'd like to implement a callback that takes two references to
> std::string and returns a bool via a Functor.
> But I can't find a function that wraps a matching member function call
> (if I understand the naming scheme correctly, this should be something
> like 'osgTypedMethodFunctor2ObjRef').
>
> Am I missing something or do I have to use the pointer variant given below?
>
> // what I want
> TypedFunctor2Base<
> bool, RefCallArg< std::string const >, ArgsCollector< std::string& >
> > callbackWithRef;
>
> // what I can get to work
> TypedFunctor2Base<
> bool, PtrCallArg< std::string const >, ArgsCollector< std::string& >
> > callbackWithPtr;
>
>
> // works with CallbackWithPtr
> bool takesPtr( std::string const* arg1, std::string& arg2 )
> { return true; }
>
> // works with CallbackWithRef
> bool takesRef( std::string const& arg1, std::string& arg2 )
> { return true; }
>
> struct S
> {
> // works with CallbackWithPtr
> bool takesPtr( std::string const* arg1, std::string& arg2 )
> {return true;}
>
> // works not with CallbackWithRef?
> bool takesRef( std::string const& arg1, std::string& arg2 )
> {return true;}
> } s;
>
> // this works
> callbackWithPtr = osgTypedMethodFunctor2ObjPtr<
> bool, S, std::string const, std::string&
> >( &s, &S::takesPtr );
>
> // can't find this function...
> callbackWithRef = osgTypedMethodFunctor2ObjRef<
> bool, S, std::string const, std::string&
> >( &s, &S::takesRef );
I've always had a bit of a hard time understanding the functors, so take
the following with a grain of salt. The first argument to a functor is
somewhat special, because the functor may wrap a member function in
which case the first argument is the object to use as "this" for the
member function call. Of course, if you wrap a free function the first
argument is just like any other.
I also believe that when wrapping member functions you are limited to
those with a single argument, since that already requires both argument
slots (one for the object to call the function on, one for the real
argument).
If you are using this in your own code I'd highly recommend using
boost::function and boost:bind, they let you do the same thing (and
more), with much easier syntax and without the limitations of OpenSG's
functors.
regards,
Carsten
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