首先，你的牌组是不可变的.请记住，rust 绑定默认是不可变的:

First, your deck is not mutable. Remember in rust bindings are non-mutable by default:

let mut deck: [Option<Card>; 52] = [None; 52];

接下来，要获得可以修改的迭代器，请使用iter_mut():

Next, to obtain an iterator you can modify, you use iter_mut():

for i in deck.iter_mut() {

最后:循环中的i 是对deck 元素的可变引用.要将某些内容分配给引用，您需要取消引用它:

Finally: the i that you have in your loop is a mutable reference to the elements of deck. To assign something to the reference, you need to dereference it:

*i = Some(Card {
    card_num: 1,
    card_suit: Suits::Hearts,
});

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