C++ function pointer callback mechanism

In C, the callback mechanism is implemented through function pointers. A function pointer points to a function whose signature is the same as the pointed-to function. Implementing callbacks includes declaring a function pointer type that matches the callback function signature. Define a callback function with a signature matching the function pointer type. Assign the callback function address to the function pointer. When calling other functions, pass function pointers as arguments.

C Callback mechanism of function pointer

The callback mechanism is a software design pattern that allows a function to be called after being called by other functions. Execute additional code. In C, callbacks can be implemented using function pointers.

Function pointer

A function pointer is a pointer to a function. It has a type that has the same signature as the function being pointed to. To declare a function pointer, use the following syntax:

typedef return_type (*function_pointer_type)(parameters);

Where return_type is the return type of the pointed function, and parameters is the parameter list of the pointed function.

Use function pointers to implement callbacks

In order to use function pointers to implement callbacks, you need to perform the following steps:

1. Declare a function pointer type, The type matches the signature of the callback function.
2. Define a callback function whose signature matches the function pointer type.
3. Assign the address of the callback function to the function pointer.
4. When calling other functions, pass the function pointer as a parameter.

Practical case

The following example demonstrates how to use function pointers to implement callbacks in C:

// 定义回调函数的签名
typedef void (*callback_function_type)(int);

// 定义回调函数
void callback_function(int i) {
    std::cout << "回调函数被调用，参数为 " << i << std::endl;
}

// 定义主函数
int main() {
    // 声明一个函数指针，指向回调函数
    callback_function_type callback = callback_function;

    // 调用其他函数并传递回调函数指针
    other_function(callback);

    return 0;
}

In this example, callback_function_type is the signature of a callback function, callback_function is a callback function, and callback is a function pointer pointing to callback_function. other_function() is an other function that calls the callback function.

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