typedef
为一个已有的类型取一个新的名字
- 基础数据类型
- 结构体类型
#include <iostream>
using namespace std;
typedef int Age;
int main() {
Age age = 20; // typedef int Age;
cout << age << endl;
return 0;
}
20
enum
枚举类型
#include <iostream>
using namespace std;
int main() {
enum days {
one, two = 2, three
} day;
day = one;
cout << day << endl;
cout << three << endl; // 从自定义的数字开始排列
return 0;
}
0
3
struct 结构体
struct 与 class 初始化
1.若类和结构体所有数据成员均为public型，可采取如下带花括号形式进行初始化。
#include <iostream>
using namespace std;
// struct的成员默认是public型
struct sStudent {
int age;
string name;
};
// class的成员默认是private型
class cStudent {
public:
int age;
string name;
};
int main() {
// 若类和结构体所有数据成员均为public型，可采取如下带花括号形式进行初始化
sStudent a = {20, "Adele"}; // 结构体可以这样初始化
cout << a.age << '\t' << a.name << endl;
cStudent b = {20, "Bob"};
cout << b.age << '\t' << b.name << endl;
return 0;
}
20 Adele
20 Bob
2.若数据成员有private或protected型，或是提供了构造函数，必须使用构造函数来进行初始化。
#include <iostream>
using namespace std;
// struct的成员默认是public型
struct sStudent {
private:
int age;
string name;
public:
string school;
sStudent(int a, string n, string sch) {
age = a;
name = n;
school = sch;
}
void show() {
cout << age << '\t' << name << '\t' << school << endl;
}
};
// class的成员默认是private型
class cStudent {
int age;
string name;
string school;
public:
cStudent(int a, string n, string sch) {
age = a;
name = n;
school = sch;
}
void show() {
cout << age << '\t' << name << '\t' << school << endl;
}
};
int main() {
sStudent a = sStudent(20, "Adele", "CSU"); // 构造函数，没有new
cStudent b = cStudent(20, "Bob", "CSU");
cout << a.school << endl; // school成员是public型
a.show();
b.show();
return 0;
}
CSU
20 Adele CSU
20 Bob CSU
typedef, enum, struct 综合实例
#include <iostream>
using namespace std;
enum Sex {
male, female, other
};
string getSex(int s) {
switch (s) {
case male:
return "male";
case female:
return "female";
case other:
return "other";
default:
return "wrong sex";
}
}
char sex[3][7] = {"male", "female", "other"}; // 这种方式好些
typedef int Age;
typedef struct {
string name;
int age;
Sex sex;
} Student, *pStudent; // 有了typedef，在定义的时候可以不用些struct
int main() {
Age age = 20; // typedef int Age;
cout << age << endl;
Student stu;
stu.age = 20;
stu.name = "shuai";
stu.sex = male;
cout << "年龄：" << stu.age << endl;
cout << "姓名：" << stu.name << endl;
cout << "性别：" << stu.sex << endl;
cout << "性别：" << getSex(stu.sex) << endl;
cout << "性别：" << sex[stu.sex] << endl << endl; // 从数组中获得相应下标的元素
pStudent pStu = new Student(); // 开辟一个存放Student的空间
pStu->name = "Eric";
cout << "姓名：" << pStu->name << endl;
return 0;
}
20
年龄：20
姓名：shuai
性别：0
性别：male
性别：male
姓名：Eric
