[英]Noob boost::bind member function callback question
#include <boost/bind.hpp>
#include <iostream>
using namespace std;
using boost::bind;
class A {
public:
void print(string &s) {
cout << s.c_str() << endl;
}
};
typedef void (*callback)();
class B {
public:
void set_callback(callback cb) {
m_cb = cb;
}
void do_callback() {
m_cb();
}
private:
callback m_cb;
};
void main() {
A a;
B b;
string s("message");
b.set_callback(bind(A::print, &a, s));
b.do_callback();
}
所以我要做的是在激活b的回調時將A流“消息”的打印方法設置為cout。 我從msvc10得到了意外數量的參數錯誤。 我確定這是超級noob基本的,我很抱歉。
replace typedef void (*callback)();
with typedef boost::function<void()> callback;
綁定函數不會生成普通函數,因此您不能將其存儲在常規函數指針中。 但是, boost::function
能夠處理任何東西 ,只要它可以使用正確的簽名進行調用,這就是你想要的。 它將與函數指針或使用bind創建的仿函數一起使用。
在對您的代碼進行一些更正之后,我想出了這個:
#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <iostream>
// i prefer explicit namespaces, but that's a matter of preference
class A {
public:
// prefer const refs to regular refs unless you need to modify the argument!
void print(const std::string &s) {
// no need for .c_str() here, cout knows how to output a std::string just fine :-)
std::cout << s << std::endl;
}
};
// holds any arity 0 callable "thing" which returns void
typedef boost::function<void()> callback;
class B {
public:
void set_callback(callback cb) {
m_cb = cb;
}
void do_callback() {
m_cb();
}
private:
callback m_cb;
};
void regular_function() {
std::cout << "regular!" << std::endl;
}
// the return type for main is int, never anything else
// however, in c++, you may omit the "return 0;" from main (and only main)
// which will have the same effect as if you had a "return 0;" as the last line
// of main
int main() {
A a;
B b;
std::string s("message");
// you forget the "&" here before A::print!
b.set_callback(boost::bind(&A::print, &a, s));
b.do_callback();
// this will work for regular function pointers too, yay!
b.set_callback(regular_function);
b.do_callback();
}
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