复合结构（C++ Primer）

复合结构（C++ Primer）

使用结构体和string

使用结构体示例代码：

#include <iostream>
#include <string>
using namespace std;

struct person{
    string fn;
    string sn;
    char grade;
    int age;
};

int main(){
    person *a=new person;
    cout<<"what is your first name?";
    cin>>a->fn;
    cout<<endl;
    cout<<"what is your last name?";
    cin>>a->sn;
    cout<<endl;
    cout<<"what letter grade do you deserve?";
    cin>>a->grade;
    cout<<endl;
    cout<<"what is your age?";
    cin>>a->age;
    cout<<"Name:"<<(*a).fn<<(*a).sn<<endl;
    cout<<"Grade:"<<(char)((*a).grade+1)<<endl;
    cout<<"Age:"<<(*a).age<<endl;
    delete a;
    return 0;
}

这部分代码很好的给出了什么时候用据点运算符，什么时候用->运算符。简单来讲,当前者是结构体名时，就是用句点，当前者是指向结构体的指针时就是用->运算符。

当使用ascii码时，想要进行符号运算(*a).grade+1，符号会被转换成整数型，所以前面要加上转换类型(char)。

输出结果：

what is your first name?wuqing

what is your last name?maliao

what letter grade do you deserve?A

what is your age?23
Name:wuqingmaliao
Grade:B
Age:23

不使用new来分配内存，同时也不使用string而是用char数组，实例代码：

#include <iostream>
using namespace std;

struct person{
    char fn[20];
    char sn[20];
    char grade;
    int age;
};

int main(){
    person a;
    cout<<"what is your first name?";
    cin>>a.fn;
    cout<<endl;
    cout<<"what is your last name?";
    cin>>a.sn;
    cout<<endl;
    cout<<"what letter grade do you deserve?";
    cin>>a.grade;
    cout<<endl;
    cout<<"what is your age?";
    cin>>a.age;
    cout<<"Name:"<<a.fn<<a.sn<<endl;
    cout<<"Grade:"<<(char)(a.grade+1)<<endl;
    cout<<"Age:"<<a.age<<endl;
    return 0;
}

结构体数组

定义一个结构体，声明结构体数组并初始化。

示例代码：

#include <iostream>
#include <string>
using namespace std;

struct  CandyBar
{
    string name;
    double weight;
    int kaLuLi;
};

int main(){
    CandyBar a[3]={{"A",12.3,8},{"B",50.6,76},{"C",54.9,126}};
    for(int i=0;i<3;i++){
        cout <<a[i].name<<" ";
        cout <<a[i].weight<<" ";
        cout <<a[i].kaLuLi<<endl;
    }
    return 0;
}

运行结果：

A 12.3 8
B 50.6 76
C 54.9 126

使用new来为结构分配内存：

#include <iostream>
#include <string>
using namespace std;

struct  CandyBar
{
    string name;
    double weight;
    int kaLuLi;
};

int main(){
    CandyBar *b[3]={new CandyBar, new CandyBar, new CandyBar };
    for(int i=0;i<3;i++){
        b[i]->name="a";
        b[i]->weight=36.8+i;
        b[i]->kaLuLi=23+i;
    }
    for(int i=0;i<3;i++){
        cout <<b[i]->name<<" ";
        cout <<b[i]->weight<<" ";
        cout <<b[i]->kaLuLi<<endl;
    }
    delete b[3];
    return 0;
}

运行结果：

a 36.8 23
a 37.8 24
a 38.8 25