The problem is that the parameter binding that you are providing has type
DummyResponse* but the method you are trying to bind takes const
DummyResponse*. Even though the former is implicitly convertible to the
latter, the compiler will not consider this when selecting a template
overload. The solution is to manually cast the pointer to make it const
before calling NewCallback.
On Sun, Aug 30, 2009 at 9:29 PM, srlindemann <srlindem...@gmail.com> wrote:
>
> I've been messing with the Service interface in C++ but have hit a few
> bumps with the NewCallback method. Basically, the compiler (g++ 4.2.4
> on Ubuntu) seems to be unable to match my function call to one of the
> template overloads---it then fails when it tries to match it to the
> void(*)() signature. Is there something here I'm missing? I'm using
> protobuf-2.2.0.
>
> Source (closure_trouble.cpp):
>
> #include <google/protobuf/service.h>
>
> class DummyResponse
> {
> };
>
> class ClosureTest
> {
> public:
> void MethodWithArg(const DummyResponse* response) {}
> };
>
> int main(int argc, char* argv[])
> {
> ClosureTest ct;
> DummyResponse dr;
>
> google::protobuf::Closure* closure = google::protobuf::NewCallback
> (&ct, &ClosureTest::MethodWithArg, &dr);
> return 0;
> }
>
> Command line:
> m...@my-laptop:~/Programming/cpp/protio/protio_main/tests$ g++ -o
> closure_trouble closure_trouble.cpp
> closure_trouble.cpp: In function ‘int main(int, char**)’:
> closure_trouble.cpp:18: error: cannot convert ‘ClosureTest*’ to ‘void
> (*)()’ for argument ‘1’ to ‘google::protobuf::Closure*
> google::protobuf::NewCallback(void (*)())’
>
> Any thoughts? Thanks.
>
> (P.S. I tried a number of similar variations, such as a function
> instead of a instance method, etc. Couldn't make anything work except
> subclassing Closure.)
>
> >
>
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