函数指针  :  函数回调 动态函数调用

1.指针类型和函数类型必须一致

#import <Foundation/Foundation.h>
//int maxValue(int a,int b){
//    return a > b ? a : b;
//}
//int minValue(int a,int b){
//    return a < b ? a : b;
//}
//
//typedef int(*pFun)(int,int);//pFun是变量类型
//
//int getValue(int a,int b,pFun p){//函数定义
//    return p(a,b);
//}

///////////////1.有一学生数组,将90分以上的学?生姓 名后加上”(月薪过万)”////////////////
//struct student {
//    float score;
//    char name[50];
//};
//typedef struct student Student;
//
//void fun(char * str){//定义一个拼接字符串的函数
//    strcat(str, "月薪过万");
//}
//typedef void(* pFun2)(char *);//指针类型void 和函数类型一定要一样
//
//void changeName(Student * arr,int count,pFun2 p){
//    for (int i = 0; i < count; i++) {
//        if (arr[i].score > 90) {
//            p(arr[i].name);//函数回调相当于 fun(arr[i].name);
//        }
//    }
//}
//void printStudent(Student * arr,int count){
//    for (int i = 0; i < count; i++) {
//        printf("%.2f %s\n",arr[i].score,arr[i].name);
//    }
//}
//////////////////////////////////////////////////////////////////////////

///////////////2.学?生结构体数组,按成绩排序、按年 龄排序,按名字排序...如何实现///////////////
struct student {
    float score;
    int age;
    char name[50];
};
typedef struct student Stu;

typedef BOOL(*pFun)(Stu *,Stu *);//和位置没关系 类型,参数一样就行

typedef struct funPointer {
    char name[50];//函数名
    pFun pointer; //函数指针
}fPointer;//定义函数指针数组

BOOL scorePanduan(Stu * stu1,Stu * stu2){//成绩从高到低
    return stu1->score < stu2->score;
}
BOOL agePanduan(Stu * stu1,Stu * stu2){//年龄从小到大
    return stu1->age > stu2->age;
}
BOOL namePanduan(Stu * stu1,Stu * stu2){//名字从a到z
    return strcmp(stu1->name, stu2->name) > 0;
}

fPointer pointer[2] = {{"成绩排序",scorePanduan},{"姓名排序",namePanduan}};//给函数指针数组赋值

pFun getFunction(fPointer * arr,int count,char * str){//(函数指针数组名,函数个数,函数名)
    for (int i = 0; i < count; i++) {
        if (strcmp(arr[i].name, str) == 0) {//比较传进去的名和函数指针数组中得名 如果一样
            return arr[i].pointer;          //返回函数指针
        }
    }
    return NULL;//要有返回值
}
void sort(Stu * stu,int count,char * str){
    pFun p = getFunction(pointer, 2, str);
    for (int i = 0; i < count - 1; i++) {
        for (int j = 0; j < count - i - 1; j++) {
            if(p(&stu[j],&stu[j + 1])){//if判断中函数回调
                Stu temp = stu[j];
                stu[j] = stu[j + 1];
                stu[j + 1] = temp;
            }
        }
    }
}

void printStudent(Stu * stu,int count){
    for (int i = 0; i < count; i++) {
        printf("%.2f %d %s\n",stu[i].score,stu[i].age,stu[i].name);
    }
}

int main(int argc, const char * argv[])
{
//    pFun p = maxValue;
//    //int (*p)(int,int) = maxValue;//p保存函数maxValue的地址 p是变量名
//    int max = p(3,5);//用指针名直接调用函数
//    printf("max = %d\n",max);
//    
//    p = minValue;
//    max = p(10,3);
//    printf("%d\n",max);
    
//    int value = getValue(3, 5, maxValue);
//    printf("value = %d\n",value);
    
//////                   1.                    /////
//    Student stu[5] = {{59.9,"shenqingjun"},{99.9,"zhaoyunlong"},{91,"liuchundong"},{95,"lixiaolong"},{89.9,"liujian"}};
//    changeName(stu, 5,fun);
//    printStudent(stu, 5);
 
//////                   2.                    /////
    Stu stu[5] = {{59.9,21,"aa"},{58.9,20,"ddd"},{80,22,"ccc"},{89.9,23,"bbt"},{90,18,"drr"}};
    
    sort(stu, 5, "姓名排序");
    printStudent(stu,5);
    
    
    return 0;
}

作业:

ios学习记录 day15,布布扣,bubuko.com

ios学习记录 day15