c++ - cout 输出乱码消息行而不是实际用户 cout 语句

Question

这是我的头文件

#ifndef KINGDOM_H_
#define KINGDOM_H_

#include <string>
using namespace std;
namespace sict{
    class Kingdom {
    public:
        char m_name[32];
        int m_population;

    };
    void display(Kingdom& pKingdom);
}
#endif

这是我的cpp文件

#include <iostream>
#include <string>
#include "kingdom.h"

using namespace std;

namespace sict {

    void display(Kingdom& pKingdom) {
        cout << pKingdom.m_name << ", population " << pKingdom.m_population << endl;
    }
}

这是我最后一个cpp文件

#include <iostream>
#include "Kingdom.h"

using namespace std;
using namespace sict;

void read(sict::Kingdom&);

int main() {
    int count = 0; // the number of kingdoms in the array
    Kingdom* pKingdom = nullptr;


    cout << "==========\n"
        << "Input data\n"
        << "==========\n"
        << "Enter the number of Kingdoms: ";
    cin >> count;
    cin.ignore();

    if (count < 1) return 1;


    pKingdom = new Kingdom[count];
    for (int i = 0; i < count; ++i) {
        cout << "Kingdom #" << i + 1 << ": " << endl;
        cin >> i;
        cout << "Enter the name of the Kingdom: " << pKingdom[i].m_name;
        cin >> pKingdom[i].m_name;
        cout << "Enter the number people living in " << pKingdom[i].m_population << ": ";
        cin >> pKingdom[i].m_population;

    }
    cout << "==========" << endl << endl;

    // testing that "display(...)" works
    cout << "------------------------------" << endl
        << "The 1st kingdom entered is" << endl
        << "------------------------------" << endl;
    sict::display(pKingdom[0]);
    cout << "------------------------------" << endl << endl;


    delete[]pKingdom;
    pKingdom = nullptr;
            return 0;
}

// read accepts data for a Kingdom from standard input

void read(sict::Kingdom& kingdom) {

    cout << "Enter the name of the Kingdom: ";
    cin.get(kingdom.m_name, 32, '\n');
    cin.ignore(2000, '\n');
    cout << "Enter the number of people living in " << kingdom.m_name << ": ";
    cin >> kingdom.m_population;
    cin.ignore(2000, '\n');
}

当代码到达输入王国名称的部分时，它会提示用户回答，但在提示之前，它只是输出这样的乱码

https://i.imgur.com/MSSHgvz.png

此外，当它输入居住人数时，它还会在我输入有效数字之前输出“-842150451”。

有什么解决问题的猜测吗？

Answer 1

您的程序打印垃圾，因为变量(char[] 和 int)没有初始化。实际行为未定义。要解决此问题，您可能应该向您的类添加一个构造函数并初始化变量。

进一步阅读:

• How do C++ class members get initialized if I don't do it explicitly?
• Why do I not get compiler warning about access uninitialized member variable in ctor?

另外，当您使用std::cin 让用户将王国名称输入到固定大小的字符数组中时，他们很容易产生缓冲区溢出。这通常是不可取的。请使用std::string相反。

不鼓励使用 using namespace std;。在头文件中尤其如此。

进一步阅读:

• Why is "using namespace std" considered bad practice?

除非你有很好的理由，否则你通常不应该使用指针来动态分配对象或数组。如果需要在运行时分配数组，请使用 std::vector相反。

进一步阅读:

• What is wrong with using arrays dynamically allocated in C++?

您可能应该为您的类添加 << 和 >> 运算符的重载。那时您不需要将这些成员公开。

进一步阅读:

• What are the basic rules and idioms for operator overloading?