rust - 从对特征关联类型的引用中读取值时，如何解决 "borrowed content"错误？

Question

我有一个指向 u64 值的指针，但我无法读取它。我收到此错误:

error[E0507]: cannot move out of borrowed content
   --> /home/niko/sub/substrate/srml/system/src/lib.rs:533:32
    |
533 |             let mut aid: T::AccountId = *copy_who;
    |                                         ^^^^^^^^^
    |                                         |
    |                                         cannot move out of borrowed content
    |                                         help: consider removing the `*`: `copy_who`

如何避免“借用内容”错误？如果您无法读取它指向的任何内容，那么拥有指向变量的指针有什么意义？

impl<T: Trait> Module<T> {
    // getter for AccountId
    pub fn get_account_id(who: &T::AccountId) -> T::AccountId {
        let mut copy_who: &T::AccountId = who;
        {
            let mut aid: T::AccountId = *copy_who;
            return aid;
        }
    }
}

AccountId 定义如下:

type AccountId = u64;

Answer 1

你的问题可以简化为

trait Example {
    type AccountId;
}

fn get_account_id<T>(who: &T::AccountId)
where
    T: Example,
{
    *who;
}

error[E0507]: cannot move out of borrowed content
 --> src/lib.rs:8:5
  |
8 |     *who;
  |     ^^^^ cannot move out of borrowed content

为了编译此代码，T::AccountId 必须实现Copy:

fn get_account_id<T>(who: &T::AccountId)
where
    T: Example,
    T::AccountId: Copy,
{
    *who;
}

但这不是最灵活的解决方案。

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