What are the application scenarios of C++ function pointers?

Function pointers are used in the following scenarios: Callback function: allows another function to be executed after the function call is completed. Polymorphism: Dynamically calling different methods based on the object type. Data structure storage: Store functions in data structures so they can be called at runtime. Optimize performance, code reuse, testing and simulation, and other scenarios.

C Application scenarios of function pointers

The function pointer is a variable that points to the memory address of the function. It allows us to convert the function Passed as parameters and stored in data structures. This provides great flexibility and is particularly useful in the following scenarios:

1. Callback function

A callback function is a function that is called after another function has completed. function to execute. Function pointers allow us to specify callback functions when the function is created, rather than waiting until the function is called.

// 定义回调函数类型
typedef void (*CallbackFunc)(int);

// 用于注册回调函数
void RegisterCallback(CallbackFunc callback) {
    // 将回调函数指针存储在某个数据结构中
}

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

    // 将回调函数指针注册到 RegisterCallback 函数
    RegisterCallback(MyCallback);

    // 调用已注册的回调函数
    InvokeCallback(10);

    return 0;
}

2. Polymorphism

Function pointers can be used to achieve polymorphism, which allows us to dynamically call different methods based on the object type.

class Animal {
public:
    virtual void Speak() = 0;
};

class Dog : public Animal {
public:
    void Speak() override {
        std::cout << "汪汪！" << std::endl;
    }
};

class Cat : public Animal {
public:
    void Speak() override {
        std::cout << "喵喵！" << std::endl;
    }
};

int main() {
    // 通过函数指针调用不同对象的 Speak() 方法
    typedef void (*SpeakFunc)(Animal*);

    Animal* dog = new Dog();
    Animal* cat = new Cat();

    SpeakFunc speak = &Animal::Speak;
    speak(dog);  // 输出："汪汪！"
    speak(cat);  // 输出："喵喵！"

    delete dog;
    delete cat;

    return 0;
}

3. Storage in data structures

Function pointers can be used to store functions in data structures such as linked lists and trees. This allows us to dynamically find and call specific functions at runtime.

4. Other scenarios

• #Optimize performance: Function pointers can be used to implement lazy calculations and avoid unnecessary function calls.
• Code reuse: Function pointers allow us to encapsulate common functionality into reusable components.
• Testing and simulation: Function pointers allow us to easily replace function implementations in testing and simulation scenarios.

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