c++ - How does libsigc++ convert a function into a slot? -


i'm working basic signal code, , can't figure out how function passed in argument. came across code in libsigc++ tutorial:

aliendetector mydetector; mydetector.signal_detected.connect( sigc::ptr_fun(warn_people) );

aliendetector has member variable:

sigc::signal<void> signal_detected;

and warn_people function simple print statement:

void warn_people() { printf("they're here!\n"); }

is there example in standard library of using function this? how compiler understand "look for" function being passed in?

it use function pointer. wikipedia has sample code in c: https://en.wikipedia.org/wiki/function_pointer#example_in_c

function pointers useful when actual function call might not known until runtime. instance:

typedef void (*callback_func)(int); callback_func foo_func;  void set_foo_func(callback_func callback) {   foo_func = callback; }  void call_foo_func() {   foo_func(5); }  void my_func(int a) {    ... }  int main() {    set_foo_func(my_func);    call_foo_func();     return exit_success; }

dereferencing optional (or meaningless, depending on how think it) , prefer it:

void call_foo_func() {   (*foo_func)(5); }  set_foo_func(&my_func);

that's static function. it's little more complicated member functions. , libsigc++ has lots of complicated code lots of useful things.


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