c++ - 什么需要在构造函数中，什么需要在 setter 函数中？

Question

目标是输出与第一个程序相同的数据。第一个程序需要手动输入房号和房费。第二个(有问题的)程序要求它自动填充房间号和房间成本，这些房间号和房间成本被硬编码到 main 中的数组中。需要类“room”的默认构造函数来填充数组并添加 setter 函数来设置房间号和成本的值。整个程序的目标是创建数组，填充测试数据，然后列出有关房间的数据。程序 1(手动输入)- 这很好用；

#include<iostream>
using namespace std;

class room 
{
    int roomNo;
    float roomCost;
public:    
    void GetData ();        
    void PutData ();        
};
void room::GetData ()   
{
    cout << "\n\tEnter room number : ";
    cin >> roomNo;
    cout << "\n\tEnter room cost : ";
    cin >> roomCost;
} 
void room::PutData ()       
{
    cout << "\n\t\t\t" << roomNo << " \t|\t " << roomCost;
} 

int main () 
{
    int roomNo;

    room roomList[10];  

    for (roomNo = 0; roomNo < 10; roomNo++)
    {
        cout << "\nEnter details of " << roomNo + 1 << " room" << endl;
        roomList[roomNo].GetData ();
    }
    cout <<"\n*******************************************************************************";
    cout << "\n\t\t\t   Room Details";
    cout <<"\n*******************************************************************************";
    cout << "\n\t\t Room Number \t|     Cost per Night";
    cout << "\n\t\t--------------------------------------";
        for (roomNo = 0; roomNo < 2; roomNo++)
        roomList[roomNo].PutData();     

    getchar ();
    getchar ();
}

第二个(有问题的)程序；

#include<iostream>
using namespace std;

class room 
{
    int roomNo;
    float roomCost;
public:
    room();
    void PutData ();        
};
room::room()
{
    cout<<"\n\t\t\t"<<roomNo<<" \t|\t "<<roomCost;
}
void room::PutData ()       
{
    cout << "\n\t\t\t" << roomNo << " \t|\t " << roomCost;
} 

int main () 
{
    int roomNo[10] = {1,2,3,4,5,6,7,8,9,10};
    float roomCost[10] = {100.00, 90.00, 85.50, 80.00, 80.00, 50.00, 50.00, 45.50, 45.50, 40.00};

    room roomList[10];  //Statement 3 : Creating Array of 3 Employees

    cout <<"\n*******************************************************************************";
    cout << "\n\t\t\t   Room Details";
    cout <<"\n*******************************************************************************";
    cout << "\n\t\t Room Number \t|     Cost per Night";
    cout << "\n\t\t--------------------------------------";

    for (int roomNo = 0; roomNo < 10; roomNo++)
    roomList[roomNo].PutData();

    getchar ();
    getchar ();
}

Answer 1

问题是 roomNo 和 roomCost 实际上从未为每个 room 实例设置任何值。该类不会自动从您在 main 中定义的数组中提取数据。

此外，

roomList[roomNo].PutData();

访问未初始化的数据:

void room::PutData ()       
{
    cout << "\n\t\t\t" << roomNo << " \t|\t " << roomCost;
} 

(构造函数有同样的问题)

解决方案是用正确的数据初始化每个房间。我建议使用构造函数:

room(int _roomNum, float _roomCost) : roomNo(_roomNum), roomCost(_roomCost)
{}

然后使用一个vector来初始化(而不是room roomsList[10])

std::vector<room> rooms;
rooms.reserve(10);
for(size_t i = 0; i < 10; ++i)
   rooms.emplace_back(roomNo[i], roomCost[i]);

Live Demo