What is the purpose and usage of function pointers in the C language?

2 years ago
Sophia Anderson
1 minute

A function pointer is a pointer variable that points to a function, which can be used to store the address of a function. The purpose and usage of function pointers are as follows:

  1. Effect:
  1. Functions can be passed between functions and used as parameters in another function, achieving callback functions.
  2. Dynamic function invocation can be achieved, where different functions are called based on different conditions.
  3. Function polymorphism can be achieved by using function pointers to call different functions to achieve different functionalities.
  1. Usage:
  1. Declare a function pointer: return type (*pointer variable name)(parameter list)
  2. Assigning a function address: pointer variable name = function name or pointer variable name = &function name.
  3. To call a function through a function pointer:
    (*pointer variable name)(parameter list) or pointer variable name (parameter list)

Example code:

#include <stdio.h>

void hello() {
    printf("Hello, world!\n");
}

void goodbye() {
    printf("Goodbye, world!\n");
}

int main() {
    void (*funcPtr)();

    funcPtr = hello;
    funcPtr(); // 调用 hello 函数

    funcPtr = goodbye;
    funcPtr(); // 调用 goodbye 函数

    return 0;
}

In this code snippet, a function pointer funcPtr is declared and assigned the addresses of the functions hello and goodbye. Finally, both functions are called by the function pointer.

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