回調函數內部的接口類導致崩潰

Question

代碼非常直截了當。如果沒有IDumb並且我將dumbClass直接傳遞給dumbWin，代碼將起作用。但是當dumbClass具有IDumb接口時，代碼崩潰在print()。

using namespace std; 

class IDumb { 
public : 
virtual void print() = 0; 
}; 

class dumbClass : public IDumb { 
public : 
void print() { 
    cout << "this is dumb class" << endl; 
} 
}; 

class dumbWin : public Fl_Window { 
IDumb *dc; 
public: 
dumbWin(IDumb *dc) : Fl_Window(100, 100, "win") { 
    Fl_Button *b = new Fl_Button(10, 10, 50, 25, "OK"); 
    b->callback((Fl_Callback*)callbk, this); 
    end(); 

    this->dc = dc; 
} 

void print() { 
    dc->print(); 
} 

static void callbk(void *p) { 
    cout << "OK" << endl; 
    ((dumbWin*)p)->print(); 
} 
}; 

int main(int argc, char **argv) 
{ 
IDumb *dC = new dumbClass(); 
dumbWin *dW = new dumbWin(dC); 
dW->show(); 

return Fl::run(); 
} 

Answer 1

您呼叫設定this->dc之前調用b->callback。這會是一個問題嗎？您最好使用成員初始化：

dumbWin(IDumb *dc) : Fl_Window(100, 100, "win"), dc(dc) 

另外，爲IDumb提供虛擬析構函數。