C++对象作为类成员

C++ objects as class members

本文关键字：成员 对象 C++      更新时间：2023-10-16

从地址制作对象并尝试引用它不起作用

Student::Student(string studentInfo_c){ // student constructor
stringstream ss(studentInfo_c);
getline(ss, lastName, ',');
getline(ss, firstName, ',');
getline(ss, address1, ',');
getline(ss, address2, ',');
getline(ss, city, ',');
getline(ss, state, ',');
getline(ss, zipCode, ',');

Address sAddrs(address1, address2, city, state, zipCode);

}
ostream& operator<<(ostream& os, const Student& s){  os << s.lastName << ", " << s.firstName << " " << s.aAddrs;
return os; // first place that sAddrs oject is referenced
}

类原型：

class Student {
private:
string line;
string lastName;
string firstName;
string address1;
string address2;
string city;
string state;
string zipCode;
public:
//Student() : Address aAddrs   this didnt work...
Student(string studentInfo_c);
string get_firstName();
string get_lastName();
void set_address(string address1_f, string address2_f, string city_f, string state_f, string zipCode_f);
friend ostream& operator<<(ostream& os, const Student& s);
~Student();

}

错误： 在函数 'std：：ostream& operator<<(std：：ostream&， const Student&('：| C：\用户\Chris\文档\2017 年夏季学期\堆操作系统\学生.cpp|67|错误："常量类学生"没有名为"aAddrs"的成员|

C：\用户\克里斯\文档\2017 年夏季学期\df\student.cpp|73|错误：在此范围内未声明"aAddrs"|

||=== 构建失败：6 个错误、0 个警告(0 分钟、0 秒(===|

附言 我知道这与其他问题相似，但它们似乎都不适合我，它们稍微先进一些。

谢谢

根据评论中的建议，我组装了一个MCVE来展示如何做到这一点：

#include <iostream>
#include <sstream>
#include <string>
using namespace std;
class Address {
private:
string address1;
string address2;
string city;
string state;
string zipCode;
public:
// default constructor (leaving contents empty)
Address() { }
// constructor.
Address(
const string &address1, const string &address2,
const string &city, const string &state,
const string &zipCode):
address1(address1), address2(address2),
city(city), state(state), zipCode(zipCode)
{ }
friend ostream& operator<<(ostream& os, const Address &a);
};
ostream& operator<<(ostream& os, const Address &a)
{
return os
<< "  Address 1: " << a.address1 << endl
<< "  Address 2: " << a.address2 << endl
<< "  City     : " << a.city << endl
<< "  State    : " << a.state << endl
<< "  Zip Code : " << a.zipCode << endl;
}
class Student {
private:
string lastName;
string firstName;
Address sAddrs;
public:
// constructor.
Student(const string &studentInfo_c);
friend ostream& operator<<(ostream& os, const Student &s);
};
Student::Student(const string &studentInfo_c)
// all members are default constructed (leaving them empty)
{
stringstream ss(studentInfo_c);
getline(ss, lastName, ',');
getline(ss, firstName, ',');
string address1, address2, city, state, zipCode;
getline(ss, address1, ',');
getline(ss, address2, ',');
getline(ss, city, ',');
getline(ss, state, ',');
getline(ss, zipCode, ',');
sAddrs = Address(address1, address2, city, state, zipCode);
}
ostream& operator<<(ostream &os, const Student &s)
{
return os
<< "Student " << s.lastName << ", " << s.firstName << endl
<< "Address: " << endl
<< s.sAddrs << endl;
}
int main()
{
string sample("Doe,John,1 Anyway,,Anytown,Anystate,12345,");
Student s(sample);
cout << s;
return 0;
}

使用 g++ 测试：

$ g++ -std=c++11 -o test test.cc
$ ./test
Student Doe, John
Address: 
Address 1: 1 Anyway
Address 2: 
City     : Anytown
State    : Anystate
Zip Code : 12345

$

笔记：

  1. Address提供了两个构造函数：一个默认构造函数和一个用于初始化的第二个构造函数。

  2. Student::Student使用默认构造函数构造所有成员。(因此，Address必须提供一个。

  3. 在Student::Student的主体中，创建一个临时的Address实例并分配给Student::sAddrs。这是因为赋值运算符(Address& Address::operator=(const Address&)(是由编译器生成的。(这不是最有效的代码，而是源代码工作量最少的代码。

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