<分区>
我没有解决显示如下的问题:student[1].allgrade[1].quiz
部分代码如下。
#include <iostream>
using namespace std;
struct grade
{ int quiz, midterm,final;
};
struct StudentRecord
{
int studentID;
double studentMark;
char letter;
struct grade allgrade[2];
} student[]={
{10,85.2,'A',{70,80,90}},{11,66,'C',{40,50,60}}
};
int main(void)
{
cout<<student[1].allgrade[1].quiz<<"\n";
return 0;
}
最佳答案
根据aggregate initialization的规则，给定初始化程序 {10,85.2,'A',{70,80,90}}，{70,80,90} 用于初始化第一个元素成员数组allgrade，然后第二个元素由空列表聚合初始化，其成员quiz，midterm 和 final 最后是值初始化。 student[1].allgrade[1].quiz 正在尝试访问 allgrade 的第二个元素的 quiz，然后你会得到 0(作为值初始化的结果)。
(强调我的)
If the number of initializer clauses is less than the number of members
and bases (since C++17)or initializer list is completely empty, the remaining membersand bases (since C++17)are initializedby their default initializers, if provided in the class definition, and otherwise (since C++14)by empty lists, in accordance with the usual list-initialization rules (which performs value-initialization for non-class types and non-aggregate classes with default constructors, and aggregate initialization for aggregates). If a member of a reference type is one of these remaining members, the program is ill-formed.
另一方面，student[1].allgrade[0].quiz 会给你结果 40。
或者您可以显式初始化第二个元素，例如
{10,85.2,'A',{70,80,90}},{11,66,'C',{{40,50,60},{10,20,30}}}
// ^^^^^^^^^^ initializer list for student[1].allgrade[1]
然后 student[1].allgrade[1].quiz 会给你结果 10。
关于c++ - C++ 中的结构与数组，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53666743/