callback c++ c
A callback in C++ is a function that is passed as an argument to another function and is called within that function. This allows the called function to execute the code in the callback function at a later point in time. Callbacks are commonly used in event-driven programming or when implementing certain design patterns.
In C, callbacks can be implemented using function pointers. A function pointer is a variable that stores the address of a function. By passing a function pointer as an argument to another function, we can specify which function should be called as a callback.
To define a callback in C++, we can use a function pointer or a lambda function. Here's an example using a function pointer:
#include <iostream>
// Callback function signature
typedef void (*Callback)(int);
// Function that takes a callback as an argument
void performOperation(int value, Callback callback) {
// Do some operation
std::cout << "Performing operation with value: " << value << std::endl;
// Call the callback function
callback(value);
}
// Callback function implementation
void callbackFunction(int value) {
std::cout << "Callback function called with value: " << value << std::endl;
}
int main() {
// Pass the callback function to performOperation
performOperation(42, callbackFunction);
return 0;
}
In this example, we define a callback function signature using the typedef
keyword. The performOperation
function takes an integer value and a callback function as arguments. Inside performOperation
, we perform some operation and then call the callback function, passing the value as an argument.
In the main
function, we pass the callbackFunction
as the callback to performOperation
. When performOperation
is called, it performs the operation and then calls the callback function, which prints the value.
This is a basic example of using callbacks in C++. Callbacks can be used in more complex scenarios, such as event handlers or asynchronous programming, to provide a way for the called function to execute custom code provided by the caller.