parent/child callback

[mhoover]

Although I can put Qt on a client, I can't put it on a server because it is running VxWorks OS (not supported by Qt).

So I have to find a way to have a child send a signal to a parent function without the signal/slot paradigm.

I'm trying to use callbacks.

I can have a member variable in the child class that points to a function, but when I try to assign it to a parent function in a parent function it gives me trouble.

I declared the callback in the child class as:

void (*callback)(void)

void (*callback)(void)

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And I try to set it in the parent class:

child->callback = (void*)handleSignal;

child->callback = (void*)handleSignal;

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It says:

error: invalid use of member (did you forget the '&' ?)

Do I just have the syntax wrong?

[mhoover]

Sheesh, I can't even get a parent callback to point to a parent method.

Here are some of the responses:

callback = blankfunc;  // error: argument of type ‘void (HadronServer::)()’ does not match ‘void (*)()’
callback = (void*)blankfunc;    // error: invalid use of member (did you forget the ‘&’ ?)
callback = (void*)blankfunc();    // error: void value not ignored as it ought to be
callback = (void*)&blankfunc();  // error: invalid lvalue in unary ‘&’
callback = (void *)test;    // error: invalid conversion from ‘void*’ to ‘void (*)()’
 
callback = &test;     // works, but test is not a member function
callback = &blankfunc;  // error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function.  Say ‘&HadronServer::blankfunc’
callback = &HadronServer::blankfunc;   // error: cannot convert ‘void (HadronServer::*)()’ to ‘void (*)()’ in assignment
callback = &((void*)blankfunc); // error: invalid use of member (did you forget the ‘&’ ?)
callback = (void *)(&blankfunc); // error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function.  Say ‘&HadronServer::blankfunc’
callback = (void *)(&HadronServer::blankfunc);   // error: converting from ‘void (HadronServer::*)()’ to ‘void*’

callback = blankfunc;  // error: argument of type ‘void (HadronServer::)()’ does not match ‘void (*)()’
callback = (void*)blankfunc;    // error: invalid use of member (did you forget the ‘&’ ?)
callback = (void*)blankfunc();    // error: void value not ignored as it ought to be
callback = (void*)&blankfunc();  // error: invalid lvalue in unary ‘&’
callback = (void *)test;    // error: invalid conversion from ‘void*’ to ‘void (*)()’

callback = &test;     // works, but test is not a member function
callback = &blankfunc;  // error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function.  Say ‘&HadronServer::blankfunc’
callback = &HadronServer::blankfunc;   // error: cannot convert ‘void (HadronServer::*)()’ to ‘void (*)()’ in assignment
callback = &((void*)blankfunc); // error: invalid use of member (did you forget the ‘&’ ?)
callback = (void *)(&blankfunc); // error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function.  Say ‘&HadronServer::blankfunc’
callback = (void *)(&HadronServer::blankfunc);   // error: converting from ‘void (HadronServer::*)()’ to ‘void*’

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So it only works when I point it at a non-member function.

[mhoover]

Ugh. It looks like this is not possible because it isn't a static function.

This website tipped me off:

http://www.codeguru.com/cpp/cpp/cpp_...cle.php/c10557

The whole reason I wanted a callback was to pass info to a parent function, but obviously I can't do that if it's a static function.