C++/inheritance and virtual functions
From Attie's Wiki
A good how-to for implementing callbacks in C++
#include <iostream> #include <string> using namespace std; /* --- */ class c1_i { public: explicit c1_i(void); ~c1_i(void); virtual void c1_callback(void) = 0; }; c1_i::c1_i(void) { cout << "c1_i::c1_i\n"; } c1_i::~c1_i(void) { cout << "c1_i::~c1_i\n"; } /* --- */ /* c2_i has no constructor / destructor functions */ class c2_i { public: virtual void c2_callback(void) = 0; }; /* --- */ /* c3_i has a constructor that takes an argument */ class c3_i { public: explicit c3_i(string message); string message; virtual void c3_callback(void) = 0; }; c3_i::c3_i(string message) { cout << "c3_i::c3_i\n"; this->message = message; } /* --- */ class myC: public c1_i, public c2_i, public c3_i { public: explicit myC(string message); ~myC(void); void c1_callback(void); void c2_callback(void); void c3_callback(void); }; myC::myC(string message): c3_i(message) { cout << "myC::myC\n"; } myC::~myC(void) { cout << "myC::~myC\n"; } void myC::c1_callback(void) { cout << "myC::c1_callback\n"; } void myC::c2_callback(void) { cout << "myC::c2_callback\n"; } void myC::c3_callback(void) { cout << "myC::c3_callback: " << message << "\n"; } /* --- */ class t1 { public: explicit t1(c1_i *i); ~t1(void); void exec(void); private: c1_i *i; }; t1::t1(c1_i *i) { if (i == NULL) throw(-1); this->i = i; cout << "t1::t1\n"; } t1::~t1(void) { cout << "t1::~t1\n"; } void t1::exec(void) { cout << "t1::exec\n"; i->c1_callback(); } /* --- */ class t2 { public: explicit t2(c2_i *i); ~t2(void); void exec(void); private: c2_i *i; }; t2::t2(c2_i *i) { if (i == NULL) throw(-1); this->i = i; cout << "t2::t2\n"; } t2::~t2(void) { cout << "t2::~t2\n"; } void t2::exec(void) { cout << "t2::exec\n"; i->c2_callback(); } /* --- */ class t3 { public: explicit t3(c3_i *i); ~t3(void); void exec(void); private: c3_i *i; }; t3::t3(c3_i *i) { if (i == NULL) throw(-1); this->i = i; cout << "t3::t3\n"; } t3::~t3(void) { cout << "t3::~t3\n"; } void t3::exec(void) { cout << "t3::exec\n"; i->c3_callback(); } /* --- */ int main(int argc, char *argv[]) { myC m("howdy"); m.c1_callback(); m.c2_callback(); m.c3_callback(); t1 t(&m); t.exec(); t2 tt(&m); tt.exec(); t3 ttt(&m); ttt.exec(); cout << "hi\n"; return 0; }
Expected output
$ g++ test.cpp -o test && ./test c1_i::c1_i c3_i::c3_i myC::myC myC::c1_callback myC::c2_callback myC::c3_callback: howdy t1::t1 t1::exec myC::c1_callback t2::t2 t2::exec myC::c2_callback t3::t3 t3::exec myC::c3_callback: howdy hi t3::~t3 t2::~t2 t1::~t1 myC::~myC c1_i::~c1_i