Question

如何访问在另一个结构中定义的结构的成员？
假设我们有一个结构定义为：

struct FR {
    size_t n;
    struct FR_1{
        unsigned char r;
        unsigned char g;
        unsigned char b;
    };
};

在2015年视觉工作室下，写作：

    struct FR x;
    x.FR_1.

不显示FR_1成员的选项。另一方面，写作：

struct FR_1 y; 说：Error,incomplete type is not allowed.

你如何处理这种结构？

Answer 1

示例声明类型struct FR_1，不是该类型的成员。相反，尝试：

struct FR {
    size_t n;
    struct FR_1 {
        unsigned char r;
        unsigned char g;
        unsigned char b;
    } fr1;
};

FR x;
x.fr1.r = 0;

Answer 2

struct FR {
    size_t n; // < Declaration of member variable
    struct FR_1{ // < Declaration of nested type
        unsigned char r;
        unsigned char g;
        unsigned char b;
    };
    FR_1 fr1; // < Declaration of member variable
};

您需要在FR_1 structrure中声明FR类型的变量，而不仅仅是类型本身。

FR fr;
fr.fr1.r = 0;

Answer 3

您需要实际创建结构的实例。正常的struct声明遵循表格

struct struct-name {
    members
} inst;

所以你需要将其声明为

struct FR {
    size_t n;

    struct FR_1 {
        unsigned char r;
        unsigned char g;
        unsigned char b;
    } fr1;
};

现在你可以写

了

FR fr;
fr.fr1.r = 255;
. . .

C ++中结构中的结构

3 个答案: