assign_in_container.cpp

#include <iostream>
#include <string>
#include <utility>
#include <future>
#include <mutex>
#include <random>
#include <thread>
#include <chrono>
#include <sstream>

using namespace std;

chrono::milliseconds random_time() {
    std::mt19937_64 eng{std::random_device{}()};
    std::uniform_int_distribution<> dist{20, 200};

    return chrono::milliseconds{dist(eng)};
}

template <typename T>
class Container {
public:
    Container(T& value)
        : ref_to_value(value)
    {}

    T& ref_to_value;
};

class MyClass {
public:
    MyClass(string text)
        : value(text)
    {}

    Container<string> GetContainer() {
        return {value};
    }

private:
    string value;
};

#define NUM_ITERATIONS 100


int main() {
    MyClass cls("Some text");

    future<void> reader = async([&cls]() {
        string& value = cls.GetContainer().ref_to_value;
        for (size_t i = 0; i < NUM_ITERATIONS; ++i) {
            cout << "Value (" << i << "): " << value << '\n';
            this_thread::sleep_for(chrono::microseconds(random_time()));
        }
    });

    future<void> writer1 = async([&cls]() {
        for (size_t i = 0; i < NUM_ITERATIONS / 2; ++i) {
            stringstream ss;
            ss << "A new string 1-" << i;
            this_thread::sleep_for(chrono::microseconds(random_time()));
            cls.GetContainer().ref_to_value = move(ss.str());
            cout << "Value updated to 1-" << i << '\n';
        }
    });

    future<void> writer2 = async([&cls]() {
        for (size_t i = 0; i < NUM_ITERATIONS / 2; ++i) {
            stringstream ss;
            ss << "A new string 2-" << i;
            this_thread::sleep_for(chrono::microseconds(random_time()));
            cls.GetContainer().ref_to_value = move(ss.str());
            cout << "Value updated to 2-" << i << '\n';
        }
    });
    
    writer1.get();
    writer2.get();
    reader.get();
    return 0;
}