C++ 在单独的线程中调用 class 方法

Question

Say, I have a class with two methods: a main thread and a separate one.

#include <iostream>
#include <chrono>
#include <thread>

using namespace std;

class Foo
{
    bool is_ready;
public:
    Foo()
    {
        is_ready = false;
    }

    void async_func()
    {
        this_thread::sleep_for(chrono::milliseconds(2000));  // do some long stuff
        is_ready = true;
    }

    void main_thread_func()
    {
        thread t([&] (Foo* foo) { foo->async_func(); }, this);
        t.join();
        
        while(true)
        {
            cout << is_ready << endl;
            this_thread::sleep_for(chrono::milliseconds(100));
        }
    }
};

int main()
{
    Foo foo;
    foo.main_thread_func();
    return 0;
}

I want to see a message with the "is_ready" state to learn the progress of another thread's function. Actually, I can see messages only when it make "true".

How to see all the progress not waiting when the function stops?

Answer 1

You call the join function before while so main thread is waiting to finished the created thread. You should call join function in right place for example after while(true).