Question

我发现我的程序有些bug，原因是因为我可以从类数组中访问数据

这是类代码

void Date::initialize(){
string monthNames[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
int monthDays[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
};

这是头文件Date.h，上面的代码存储在Date.cpp中并使用main.cpp加载它

class Date{
private:
int day;
int month;
int year;
string monthNames[12];
int monthDays[12];

Answer 1

void Date::initialize()
{
     string monthNames[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
     copy(monthNames, monthNames + 12, this->monthNames);
}

您创建一个本地数组，这是合乎逻辑的，因为您只能使用大括号初始化数组，而不能分配给它。所以你创建了一个本地数组。现在您需要将其复制到您的实际成员this->monthNames。对于另一个阵列也是如此。看一下copy函数。如果不允许使用stl算法，则可以使用旧的for循环进行复制。

Answer 2

您刚刚定义了局部变量，因此您必须将其数据复制到初始化类属性。

void Date::initialize(){
    // make the data static not to initialize them every time this function is called
    static string monthNamesData[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
    static int monthDaysData[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    for (size_t i = 0; i < sizeof(monthNames) / sizeof(*monthNames); i++){
        monthNames[i] = monthNamesData[i];
    }
    for (size_t i = 0; i < sizeof(monthDays) / sizeof(*monthDays); i++){
        monthDays[i] = monthDaysData[i];
    }
}

Answer 3

数组monthNames和monthDays被声明为成员函数initialize

的局部变量

void Date::initialize(){
string monthNames[] = 
^^^^^^^^^^^^^^^^^^^
{"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
int monthDays[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
^^^^^^^^^^^^^^^
};

退出函数后会将其销毁。

尝试改为

#include <array>

//...

class Date{
private:
int day;
int month;
int year;
std::array<string, 12> monthNames;
std::array<int, 12> monthDays;

//...

void Date::initialize(){
monthNames = { {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"} };
monthDays = { {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31} };
};

Answer 4

私有成员变量只能通过PUBLIC成员函数在其类外部访问（但此函数的声明必须在我认为您已经完成的类中）。你的initialize（）函数是公开的吗？因为我不这么认为。对于Classes，一切都是PRIVATE BY DEFAULT，所以请确保你的initialize（）在class中声明，但在PUBLIC标题下。

无法从类数组访问数组

4 个答案: