c++ - function array with functions from different objects -
i don't have experience using array of functions in c++. need use array of functions array contains functions different objects. here dummy code illustrate want implement.
class base_class { public: virtual int function1(int arg1, int arg2); virtual int function2(int arg1, int arg2); }; class derived_class : public base_class { public: int function1(int arg1, int arg2) { /* ... */ }; int function2(int arg1, int arg2) { /* ... */ }; // ... }; typedef int (*functions) (int arg1, int arg2); int main() { derived_class object1; derived_class object2; functions func_instance[4]; func_instance[0] = object1.function1; func_instance[1] = object1.function2; func_instance[2] = object2.function1; func_instance[3] = object2.function2; // ... } i can't work, throws following error:
error: argument of type int () (int , int) not match int (*) (int, int)
the easiest way use std::function , std::bind.
#include <functional> #include <array> derived_class object1; derived_class object2; std::array< std::function<int(int, int)>, 2> > arr = {{ std::bind(&derived_class::function1, &object1) , std::bind(&derived_class::function2, &object1)}}; // , on note object1 , object2 have been bound address. need keep them alive long bound functions alive. if write object1 in bind expression copy of object stored in bound function , no scope problems occur.
c++03 complete example hand-rolled, single-purpose binder-type:
#include <iostream> struct base { virtual void f0() { std::cout << "f0 base" << std::endl; } virtual void f1() { std::cout << "f1 base" << std::endl; } }; struct derived : base { void f0() { std::cout << "f0 derived" << std::endl; } void f1() { std::cout << "f1 derived" << std::endl; } }; // typedef pointer member function // of base accepts arguments , returns void typedef void (base::*memberptrtype)(void); // pack pointer class , pointer member function struct binder { memberptrtype ptr; base* base; // shortcut call thing, might want // have overload of operator() , result_type typedef void call() { ((base)->*(ptr))(); } }; int main() { base b; derived d; // initialize 4 element array of binder, first argument function, // second object call on // // remember b , d need alive long // want call in array binder arr[4] = { {&base::f0, &b}, {&base::f1, &b}, {&base::f0, &d}, {&base::f1, &d}}; // walk through array , call each for(binder* begin = arr; begin != arr + 4; ++begin) { begin->call(); } return 0; }
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