In recent years, C++ has been evolving rapidly with the addition of many exciting features. One such feature is coroutines, which provide a powerful and efficient way to write asynchronous code. Coroutines enable developers to write code that looks like traditional sequential code, but runs asynchronously in the background. In this blog post, we will explore how we can utilize C++ coroutines to build desktop applications.

What are C++ Coroutines?

C++ coroutines are a language feature that allows developers to write asynchronous code in a more readable and maintainable way. Before coroutines, writing asynchronous code in C++ usually involved complex and convoluted callbacks or manual state machines. Coroutines simplify this process by allowing developers to write asynchronous code in a more sequential and natural way.

Building Desktop Applications

Desktop applications often need to perform time-consuming operations such as network requests or file I/O. Traditionally, these operations would block the main thread, making the user interface unresponsive. With coroutines, we can easily offload these operations to the background, keeping the application responsive and providing a smooth user experience.

Let’s take a look at an example of how we can use coroutines to fetch data from a server and update the user interface in a desktop application:

#include <cppcoro/task.hpp>
#include <cppcoro/when_all.hpp>

cppcoro::task<std::string> fetchDataFromServer()
{
    // Simulate a network request delay
    co_await std::chrono::seconds(1);

    co_return "Data from server";
}

cppcoro::task<void> updateUI(const std::string& data)
{
    // Update the user interface with the fetched data
    std::cout << "Updating UI with: " << data << std::endl;

    co_return;
}

cppcoro::task<void> main()
{
    // Fetch data from server and update UI concurrently
    auto [dataTask, uiTask] = cppcoro::when_all(
        fetchDataFromServer(),
        updateUI("Loading...")
    );

    co_await dataTask;
    co_await uiTask;
}

int main()
{
    cppcoro::sync_wait(main());

    return 0;
}

In the above code, we define two coroutine functions fetchDataFromServer() and updateUI(). The fetchDataFromServer() function simulates a network request delay and returns the fetched data. The updateUI() function updates the user interface with the fetched data.

In the main() coroutine function, we use the cppcoro::when_all() function to asynchronously execute both the fetchDataFromServer() and updateUI() functions concurrently. By using co_await, we can wait for the completion of each task. Finally, we use cppcoro::sync_wait() to run the main() coroutine in a synchronous fashion.

Conclusion

C++ coroutines provide a powerful tool for building desktop applications that require asynchronous operations. By using coroutines, we can write more readable and maintainable code while keeping the user interface responsive. If you’re starting a new desktop application project or looking to refactor an existing one, consider leveraging the power of C++ coroutines for a better development experience.

#cpp #coroutines