c - C- Structure within structure

Question

If i have these structures:

struct rec {
 int key;
 double value;
};

struct node {
 struct rec record;
 struct node *next;
};

and I have to copy the values of the fields of an item struct rec *r into an item struct node *n,

can i do this?

n->record.key = r->key;
n->record.value = r->value;

score 5 · Accepted Answer

是的，您可以一次复制struct一个字段。您也可以一次性完成：

struct rec *r = ...;
struct node *n = ...;
n->record = *r; // Copies the content of "r" into n->record

这样做的好处是不必在每次修改struct rec.

score 2 · Accepted Answer

由于该rec结构仅包含基本类型的字段，因此这样做是完全有效且合理的：

n->record = *r;

在这种情况下，这相当于分别复制key和value字段：

n->record.key = r->key;
n->record.value = r->value;

score -1 · Accepted Answer

n->rec.key = r->key;
n->rec.value = r->value;

正确但更好的是：

memcpy(&n->rec, r, sizeof n->rec);

现在您可以在不更改现有代码的情况下使用新字段扩展 struct rec

3 回答 3