STL map - no matching constructor

Question

I have a std map that combines a string with a function pointer like:

 std::map<std::string, void (*)()> funcs {
       {"print", &h::print},
       {"scan", &h::scan_cmd},
       {"connect", &h::stream},
       {"stream", &h::stream}
 };

where h is the enclosing class in which this map has been initialized:

class h {
public:
   void print();
   void scan();
   void connect();
   void stream();
   std::map<std::string, void (*)()> funcs {
           {"print", &h::print},
           {"scan", &h::scan_cmd},
           {"connect", &h::stream},
           {"stream", &h::stream}
     };
};

I get this error:

No matching constructor for initialization of 'std::map<std::string, void (*)()>' (aka 'map<basic_string<char>, void (*)()>')

I've also tried puttting the map in this form:

std::map<std::string, void (*)()> funcs;
funcs["print"] = &print;
funcs["scan"] = &scan_cmd;
funcs["connect"] = &stream;
funcs["stream"] = &stream;

But then I got this error:

Size of array has non-integer type ' const char [6]'

I'm not exactly sure where the problem is - my guess is that it's with the void (*) () portion. I'm sure this is a c++ 11 compiler.

Are you sure you have a C++11 compiler? Also, your code is broken around "connect" (mismatched quotation marks?). — Kerrek SB
– Kerrek SB, Commented Feb 20, 2019 at 20:44
(void connect(); void stream();…"connect", &h::stream}, looks funny as does funcs["connect"] = &stream;.) — greybeard
– greybeard, Commented Feb 20, 2019 at 21:19

rafix07 · Accepted Answer · 2019-02-20 21:46:58Z

1

void (*)()

is pointer to ordinary function which takes no arguments and returns no value. In your example print, stream, scan_cmd are non-static member functions of h class. Syntax to define pointer to member functions of h class looks like

void (h::*)()

Try:

   std::map<std::string, void (h::*)()> funcs {
           {"print", &h::print},
           {"connect", &h::stream},
           {"stream", &h::stream}
     };

answered Feb 20, 2019 at 21:46

rafix07

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