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在头文件中声明一个类，并从用户输入初始化该类的数组

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请参阅下面我的c代码片段 . 因为foo.h是在int main（int argc，char * argv []）之前执行的，所以数组RedApple将初始化为0并导致错误 . 处理这个问题的最佳方法是什么？有没有办法在foo.h中保留类声明，但是从用户输入中在foo.cpp中初始化它？谢谢！

在foo.h中

#include <vector>
extern int num;
class apple
{
std::vector<long> RedApple;
public:
    apple(): RedApple(num)
}

在foo.cpp中

#include    "foo.h"
int num;
int main(int argc, char *argv[])
{
sscanf_s(argv[1],"%d",&num);
}
c++ arrays

1 回答

  • 1

    在foo.h中

    #include <vector>

class apple
{
std::vector<long> RedApple;
public:
    apple(){}
    apple(int num): RedApple(num){}
}

    在foo.cpp中

    #include    "foo.h"

int main(int argc, char *argv[])
{
    int num;
    sscanf_s(argv[1],"%d",&num);

    apple foo = num > 0 ? apple(num) : apple();
}

    EDIT: 为了回应Klaus ' complaint I thought I' d添加初始化的解释，我正在评论 apple foo = num > 0 ? apple(num) : apple(); 行，所以我会在每个单词上对它进行垂直评论：

    apple      // This is the type of variable in the same way int is the type of int num;
foo        // The name of the apple object that I am creating
=          // Normally this will trigger the assignment operator (but in a declaration line the compiler will optimize it out)
num > 0 ?  // The condition to a ternary operator if true the statement before the : is executed if false the one after is executed
apple(num) // If num is greater than 0 use the non-default constructor
: apple(); // If num is less than or equal to 0 use the default number cause we can't initialize arrays negatively
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