函数指针
是一个指针，指向函数的指针，指针存放的都是地址，所以函数指针存放的是函数的地址。数组名就是数组的首地址，函数名就是函数的首地址。与数组类似。
代码demo
int (*p) (int ,int ) = NULL; // int (*) (int ,int ) 这就是指针变量的类型 (除了函数名)
p = maxValue; 指针变量存储的是函数的地址（函数名） // 定义一个有两个整形参数且返回为整型的函数指针
#import <Foundation/Foundation.h> // 求两个数字的最大值
// 函数的类型就是由 返回值类型 + 参数个数及类型
int maxValue(int , int );
int maxValue(int a , int b ){
return a > b ? a :b ;
}
int minValue(int ,int );
int minValue(int a, int b){
return a < b ? a : b;
}
//char getString(); 不能这样写
char *getString();//类型 char * 函数名 getString 返回值类型为 char * 而且没有参数的函数
char *getString(){
// char a[10] = "hello";
char *a = "hello";
return a;
} void outputNumber(int a); // 类型 void （）
void outputNumber(int a){//void * 是一个泛型 返回泛型的指针 ？？？
printf("\noutputNumber 输出传入数字 %d\t",a);
} // 定义一个函数求两个浮点数的和
float requireTwoFloatSum(float a, float b);
float requireTwoFloatSum(float a, float b){
return a + b;
}
int main(int argc, const char * argv[]) { // 定义一个有两个整形参数且返回为整型的函数指针
int (*p) (int ,int ) = NULL;
// int (*) (int ,int ) 这就是指针变量的类型 (除了函数名)
p = maxValue; // 指针变量存储的是函数的地址（函数名）
int value = p (,);
printf("\nvalue = %d \t",value);
int (*p0) (int , int ) = NULL;
p0 = minValue;
int min = p0( , );
printf("\n min = %d\n",min); // 分别定义函数指针，来指向对应的函数，然后使用此指针实现函数的调用
// char (*p1) = NULL;
// p1 = getString;
char * str = getString();//没有参数小括号 不能省略
// 练习：分别定义函数指针，来指向对应的函数，然后使用此指针实现函数的调用
char *(*p1)() = NULL; //第二个 * 是标记 p1 是一个指针 p1的类型是char *(* )()
printf("%s\t",str); // outputNumber 输出传入数字
int (*p2)(int) = NULL;
p2 = outputNumber;
p2(); // 定义一个函数求两个浮点数的和
float (*p3)(float ,float) = NULL;
p3 = requireTwoFloatSum;
float a = p3(15.44,14.33);
printf("\n定义一个函数求两个浮点数的和 %.2f",a);
return ;
}
#import <Foundation/Foundation.h> // 定义一个函数求两个整数的和
int requireTwoSum(int a, int b);
int requireTwoSum(int a, int b){
return a + b;
} // 求两个数字的最大值
int maxValue(int , int );
int maxValue(int a , int b ){
return a > b ? a :b ;
}
// 求两个数字的最小值
int minValue(int ,int );
int minValue(int a, int b){
return a < b ? a : b;
} //函数当成一个函数形参
typedef int (*FUNCTION)(int ,int); //如果这里不写 typedef 的话， typedef FUNCTION f;这句就要报错 ，typedef 只是为数据类型重命名
//这个 FUNCTION 可以指向任意一个 int (* )(int ,int) 这种类型的函数（上面的求和，求最大值，求最小值）
typedef FUNCTION f;
int getValue(int ,int ,f );//声明了一个可以传递函数的函数
int getValue(int a ,int b ,f f1 ){
int q = f1(a,b);
return q;
} int main(int argc, const char * argv[]) { int arr = getValue(, , maxValue);
printf("maxValue = %d\t",arr);
int brr = getValue(, , minValue);
printf("minValue = % d\t",brr);
int crr = getValue(, , requireTwoSum);
printf("TwoSum = %d\t",crr); return ;
}
函数指针 demo
typedef 给结构体 与 指针函数 定义新的名字的时候，要注意 把新名字存放正确的地方。typedef 只是给数据类型重新定义名字
应用实战
#import <Foundation/Foundation.h>
#import "runSort.h"
#import "teacher.h" int main(int argc, const char * argv[]) {
/*
Student stu[5] ={
{"zhang san", 12 , 89},
{"li si", 15 , 98},
{"wang wu", 45 , 78},
{"liu guang dan ", 18, 45},
{"hei li qi", 11, 49}
};
match fun[3] = {
{compaerByAge,"age"},
{compaerByName,"name"},
{compaerByScore,"score"}
};
compareMethood pp = getFunction(fun, 2, "name");
sortArrAccending(stu, 5 ,pp);
*/
Teacher teacher[]={
{"wang ma zi",'m',,,8.9},
{"li si",'m',,,9.6},
{"huang xing",'f',,,4.9},
{"zhang ming",'f',,,},
{"zhang san",'f',,,7.5} };
match2 fun2[]={
{compareNameByAscending,"namesx"},
{compareNmaeByDescending,"namejx"},
{compareNumByAscending,"numsx"},
{compareNumByDescending,"numjx"},
{compareMarkByAscending,"marksx"},
{compareMarkByDescending,"marksx"},
};
compareMethood2 p2 = getFounction(fun2, , "numsx");
sortTeachers(teacher,,p2); return ;
}
mian
#import <Foundation/Foundation.h>
typedef struct teacher{
char name[];
char gender;
int age;
int num;
float mark;
}Teacher;
//指针函数（对比下面好多升序降序的函数）
typedef BOOL (* compareMethood2)(Teacher teacher1,Teacher teacher2) ;
typedef struct Match2{
compareMethood2 Function2;
char fname2[];
}match2;
//打印 teacher 信息
void printTeacher(Teacher * teacher);
//函数指针类型
typedef BOOL(*compareFunctionPointer)(Teacher teacher1,Teacher teacher2);
//老师数组排序函数
void sortTeachers(Teacher *teacher,int count ,compareFunctionPointer cfp);
//声明一个打印数组中所有老师的函数
void printTeachers(Teacher *teachers,int count);
//两个比较姓名的函数 升序
BOOL compareNameByAscending(Teacher teacher1, Teacher teacher2);
//降序
BOOL compareNmaeByDescending(Teacher teacher1, Teacher teacher2);
//分别声明两个比较Teacher员工编号的函数 升序
BOOL compareNumByAscending(Teacher taecher1, Teacher teacher2);
//降序
BOOL compareNumByDescending(Teacher teacher1,Teacher teacher2);
//分别声明两个比较Teacher员工评分的函数 升序
BOOL compareMarkByAscending(Teacher teacher1,Teacher teacher2);
//降序
BOOL compareMarkByDescending(Teacher teacher1,Teacher teacher2);
//声明一个输出教师数组中全部男老师的函数
void printMaleTeacher(Teacher *teacher,int count);
//声明一个输出教师数组中全部女老师的函数
void printFemaleTeacher(Teacher *teacher,int count);
//条件匹配函数
compareMethood2 getFounction(match2 * match2, int count ,char * frame2);
teacher.h
#import "teacher.h" //打印 teacher 信息
void printTeacher(Teacher * teacher){
printf("姓名: %s 性别: %c 年龄: %d 工号: %d 评分: %.2f \n",teacher->name,teacher->gender,teacher->age,teacher->num,teacher->mark);
}
//老师数组排序函数
void sortTeachers(Teacher *teacher,int count ,compareFunctionPointer cfp){
if (cfp == NULL) {
printf("没有匹配");
}else{
for (int i = ; i < count - ; i++) {
for (int j = ; j < count - - i; j++) {
if (cfp(*(teacher + j),*(teacher + j + ))) {
Teacher temp = *(teacher + j);
*(teacher + j) = *(teacher + j + );
*(teacher + j + ) = temp;
}
}
}
}
printTeachers(teacher ,count);
}
//声明一个打印数组中所有老师的函数
void printTeachers(Teacher *teachers,int count){
for (int i = ; i < count ; i++) {
printf("姓名: %s 性别: %c 年龄: %d 工号: %d 评分: %.2f \n",(teachers + i)->name,(teachers + i)->gender,(teachers + i)->age,(teachers + i)->num,(teachers + i)->mark);
}
}
//两个比较姓名的函数 升序
BOOL compareNameByAscending(Teacher teacher1, Teacher teacher2){
return strcmp(teacher1.name,teacher2.name);
}
//降序
BOOL compareNmaeByDescending(Teacher teacher1, Teacher teacher2){
return strcmp(teacher2.name, teacher1 .name);
}
//分别声明两个比较Teacher员工编号的函数 升序
BOOL compareNumByAscending(Teacher teacher1, Teacher teacher2){
return teacher1.num > teacher2.num;
}
//降序
BOOL compareNumByDescending(Teacher teacher1,Teacher teacher2){
return teacher2.num > teacher1.num;
}
//分别声明两个比较Teacher员工评分的函数 升序
BOOL compareMarkByAscending(Teacher teacher1,Teacher teacher2){
return teacher1.mark > teacher2.mark;
}
//降序
BOOL compareMarkByDescending(Teacher teacher1,Teacher teacher2){
return teacher2.mark > teacher1.mark;
}
//声明一个输出教师数组中全部男老师的函数
void printMaleTeacher(Teacher *teacher,int count){
for (int i = ; i < count; i++) {
if ((teacher + i)->gender == 'm') {
printTeacher((teacher + i));
}
}
}
//声明一个输出教师数组中全部女老师的函数
void printFemaleTeacher(Teacher *teacher,int count){
for (int i = ; i < count; i++) {
if ((teacher + i)->gender == 'f') {
printTeacher((teacher + i));
}
}
}
//条件匹配函数
compareMethood2 getFounction(match2 * match2, int count, char *fname2){
for (int i = ; i < count; i++) {
if (strcmp(match2[i].Function2, fname2)) {
return match2[i].Function2;
break;
}else{
return NULL;
}
}
return ;
}
teacher.m
#import <Foundation/Foundation.h>
typedef struct{//学生信息
char name[];
int age;
float score;
}Student;
typedef BOOL(*compareMethood)(Student,Student);
typedef struct Match{
compareMethood Function ;
char fname[];
}match;
//打印学生信息
void outputAllStuInfo(Student *stu,int count);
//升序排序信息
void sortArrAccending(Student *stu,int count ,compareMethood Condition);
//比较两者年龄
BOOL compaerByAge(Student stu1, Student stu2);
//比较两者成绩
BOOL compaerByScore(Student stu1,Student stu2);
//比较两者姓名
BOOL compaerByName(Student stu1,Student stu2);
//条件匹配函数
compareMethood getFunction(match * match ,int count , char *Fname);
runSort.h
#import "runSort.h" //打印学生信息
void outputAllStuInfo(Student *stu,int count){
for (int i = ; i < count; i++) {
printf("name = %s ,age = %d score = %.2f\n",(stu + i)->name,(stu + i)->age,(stu + i)->score);
}
} //升序排序信息
void sortArrAccending(Student *stu,int count,compareMethood Condition){
if (Condition == NULL) {
printf("没有匹配");
}else{
for (int i = ; i < count - ; i++) {
for (int j = ;j < count - - i; j++) {
if (Condition(*(stu + j),*(stu + j + ))) {
Student temp = *(stu + j);
*(stu + j ) = *(stu + j + );
*(stu + j + ) = temp;
}
}
}
}
outputAllStuInfo(stu, );
} //比较两者年龄
BOOL compaerByAge(Student stu1, Student stu2){
return stu1.age > stu2.age;
} //比较两者成绩
BOOL compaerByScore(Student stu1,Student stu2){
return stu1.score > stu2.score;
} //比较两者姓名
BOOL compaerByName(Student stu1,Student stu2){
return strcmp(stu1.name ,stu2.name);
} //条件匹配函数
compareMethood getFunction(match * match ,int count , char *Fname){
for (int i = ; i < count; i++) {
if (strcmp( match[i].Function , Fname)) {
return match[i].Function;
}else{
return NULL;
}
}
return ;
}
runSort.h