C 语言 之 面向对象（一）C 语言 之 面向对象（一）
了解C语言面向对象之前首先需要对C语言的指针、结构体有基本了解。
指针
正常使用数组：
void hello(){#define count 10// shint a[count] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, a[i]);}for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, a[i]);}printf("================================\n");int *b = malloc(sizeof(int) * 10);for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, b[i]);}free(b);b = malloc(sizeof(int) * 10);b[1] = 44;for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, b[i]);}free(b);
}
数组默认是个指针常量，无法修改指针指向，但可以修改内容
指针常量
void hello(){#define count 10// shint a[count] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, a[i]);}for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, a[i]);}printf("================================\n");int * const b = malloc(sizeof(int) * 10); // 定义指针常量for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, b[i]);}// free(b);// b = malloc(sizeof(int) * 10); b[1] = 44;for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, b[i]);}free(b);
}
指针常量const在指针名称之前，意味着指针指向不可修改
常量指针
// 【关键补充】4. Person_SetAge函数的实现（之前缺失的部分）
void Person_SetAge(Person* self, int new_age) {if (self == NULL) return; // 避免空指针访问// 可选：添加参数校验（如年龄不能为负数）if (new_age >= 0) {self->age = new_age; // 修改结构体的age成员} else {printf("Invalid age: %d (must be non-negative)\n", new_age);}
}void hello(){#define count 10// shint a[count] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, a[i]);}for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, a[i]);}printf("================================\n");// const int * b = malloc(sizeof(int) * 10); // 定义常量指针 orint const * b = malloc(sizeof(int) * 10); // 定义常量指针for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, b[i]);}free(b);b = malloc(sizeof(int) * 10); // b[1] = 44;for(int i = 0; i < count; i ++ ){printf("i: %d, value: %d\n", i, b[i]);}free(b);
}
常量指针意味着值是无法被修改的，但是你可以直接换新值。
结构体
定义结构体
// 定义结构体类型：struct Student
struct Student {char name[20]; // 姓名（字符数组）int age; // 年龄（整数）float score; // 成绩（浮点数）
};
使用结构体1
void hello(){struct Student stu1, stu2;struct Student stu3 = {"zsh",18,95.5F};struct Student stu4 = {.age = 19,.name = "zsh1",.score = 96.5F};printf("name: %s, age: %d, score: %f\n", stu1.name, stu1.age, stu1.score);printf("name: %s, age: %d, score: %f\n", stu2.name, stu2.age, stu2.score);printf("name: %s, age: %d, score: %f\n", stu3.name, stu3.age, stu3.score);printf("name: %s, age: %d, score: %f\n", stu4.name, stu4.age, stu4.score);
}
使用结构体2
void hello(){struct Student *stu1 = malloc(sizeof(struct Student));stu1->name = "zsh";stu1->age = 17;stu1->score = 95.5F;printf("name: %s, age: %d, score: %f\n", stu1 -> name, stu1 -> age, stu1 -> score);free(stu1);stu1 = NULL;
}
结构体2
使用别名
// 定义结构体类型：struct Student
typedef struct Student {char *name; // 姓名（字符数组）int age; // 年龄（整数）float score; // 成绩（浮点数）
} Student;
// or
typedef struct Student Student;
// 定义结构体类型：struct Student
struct Student {char *name; // 姓名（字符数组）int age; // 年龄（整数）float score; // 成绩（浮点数）
};
简化调用
void hello(){Student *stu1 = malloc(sizeof(Student));stu1->name = "zsh";stu1->age = 17;stu1->score = 95.5F;free(stu1);printf("name: %s, age: %d, score: %f\n", stu1 -> name, stu1 -> age, stu1 -> score);
}
给结构体定义方法
定义结构体
#ifndef LEARNC01_H
#define LEARNC01_H#include <stdio.h>
#include <stdlib.h>
#include <string.h>// 定义类型别名
typedef struct Student Student;
// 定义方法别名
/*** 方法别名类型toStringFunc,参数void,返回值void*/
typedef void (*ToStringFunc)(Student*);// 定义结构体类型：struct Student
struct Student {char *name; // 姓名（字符数组）int age; // 年龄（整数）float score; // 成绩（浮点数）ToStringFunc toString;
};// 定义方法
/*** 创建对象*/
Student* StudentCreate(const char *name, const int age, const float score);
void StudentPrint(Student* self);
void StudentDestroy(Student* self);void hello();#endif // LEARNC01_H
源文件
// ==================
Student* StudentCreate(const char* name, const int age, const float score){Student* self = malloc(sizeof(Student));if (self == NULL){printf("内存不足\n");return NULL;}const int nameLength = strlen(name);self->name = malloc(nameLength);strcpy(self -> name, name);printf("name: %s, nameLength: %d, self->name: %s, self->nameLength: %d\n", name, nameLength, self->name, strlen(self->name));self->age = age;self -> score = score;self->toString = StudentPrint; // 引用头文件方法别名,链接时指向实现方法return self;
}
void StudentDestroy(Student *self){if (self == NULL) return;free(self->name); // 先释放姓名的堆内存free(self);
}void StudentPrint(Student* self) {printf("Student(name=%s, age=%d, score=%f)", self->name, self->age, self->score);
}void hello(){Student *student = StudentCreate("zsh", 18, 95.5F);if(student == NULL){printf("student == NULL\n");return;}student->toString(student);StudentDestroy(student);
}