Registering callback using std::function in C++

Welcome to the next pikoTutorial ! Imagine you're building an application that processes some data and once it's done, the user needs to be notified about the result. Since you don’t want to hard-code the notification logic, it’s better to allow the user to register a custom function that will be called automatically after the data processing completes. Using std::function for callback registration One of the most flexible ways to implement callbacks in C++ is by using std::function. std::function can store and invoke any callable object (functions, lambdas, or function objects) that matches a specific signature. The overall syntax is: std::function name; Let’s define a ProcessData unction that accepts a callback and notifies the user once processing is complete. #include #include // Type alias for the callback type using CallbackType = std::function; // Function accepting callback as an argument void ProcessData(const CallbackType& callback) { // Simulate data processing std::cout

May 13, 2025 - 09:48

Registering callback using std::function in C++

Welcome to the next pikoTutorial !

Imagine you're building an application that processes some data and once it's done, the user needs to be notified about the result. Since you don’t want to hard-code the notification logic, it’s better to allow the user to register a custom function that will be called automatically after the data processing completes.

Using `std::function` for callback registration

One of the most flexible ways to implement callbacks in C++ is by using std::function. std::function can store and invoke any callable object (functions, lambdas, or function objects) that matches a specific signature. The overall syntax is:

std::function<function_return_type(function_argument_types)> name;

Let’s define a ProcessData unction that accepts a callback and notifies the user once processing is complete.

#include 
#include 
// Type alias for the callback type
using CallbackType = std::function<void(const bool)>;
// Function accepting callback as an argument
void ProcessData(const CallbackType& callback) {
    // Simulate data processing
    std::cout << "Processing data" << std::endl;
    // Notify user via callback
    callback(true);
}
// Callback function definition
void Callback(const bool result) {
    std::cout << "Callback called! Result: " << result << std::endl;
}

int main() {
    // Register a callback using an existing function
    ProcessData(Callback);
    // Register a callback using lambda function
    ProcessData([](const bool result) {
        std::cout << "Lambda called! Result: " << result << std::endl;
    });
    // Register using callable object
    CallbackType cb = [](const bool result){
        std::cout << "Callable called! Result: " << result << std::endl;
    };
    ProcessData(cb);
}