将指向类成员函数的指针作为参数传递 [英] Passing a pointer to a class member function as a parameter
问题描述
我写了一个小程序,我试图传递一个类的成员函数的指针到另一个函数。你能帮助我和我错了吗?
I have written a small program where I am trying to pass a pointer to member function of a class to another function. Can you please help me and where I am going wrong..?
#include<iostream>
using namespace std;
class test{
public:
typedef void (*callback_func_ptr)();
callback_func_ptr cb_func;
void get_pc();
void set_cb_ptr(void * ptr);
void call_cb_func();
};
void test::get_pc(){
cout << "PC" << endl;
}
void test::set_cb_ptr( void *ptr){
cb_func = (test::callback_func_ptr)ptr;
}
void test::call_cb_func(){
cb_func();
}
int main(){
test t1;
t1.set_cb_ptr((void *)(&t1.get_pc));
return 0;
}
我尝试编译时出现以下错误。
I get the following error when I try to compile it.
error C2276: '&' : illegal operation on bound member function expression
推荐答案
您不能将函数指针转换为 void *
。
You cannot cast a function pointer to void*
.
如果你想要一个函数指针指向一个成员函数,你必须声明类型为
If you want a function pointer to point to a member function you must declare the type as
ReturnType (ClassType::*)(ParameterTypes...)
此外,您不能声明一个指向绑定成员函数的函数指针,例如
Further you cannot declare a function pointer to a bound member function, e.g.
func_ptr p = &t1.get_pc // Error
而您必须取得如下地址:
Instead you must get the address like this:
func_ptr p = &test::get_pc // Ok, using class scope.
最后,当调用指向成员函数的函数指针时,与该函数是其成员的类的实例。例如:
Finally, when you make a call to a function pointer pointing to a member function, you must call it with an instance of the class that the function is a member of. For instance:
(this->*cb_func)(); // Call function via pointer to current instance.
下面是应用所有更改的完整示例: / p>
Here's the full example with all changes applied:
#include <iostream>
class test {
public:
typedef void (test::*callback_func_ptr)();
callback_func_ptr cb_func;
void get_pc();
void set_cb_ptr(callback_func_ptr ptr);
void call_cb_func();
};
void test::get_pc() {
std::cout << "PC" << std::endl;
}
void test::set_cb_ptr(callback_func_ptr ptr) {
cb_func = ptr;
}
void test::call_cb_func() {
(this->*cb_func)();
}
int main() {
test t1;
t1.set_cb_ptr(&test::get_pc);
t1.call_cb_func();
}
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