HashMap内部结构错误：无法移出共享引用后面的xxx [重复]

Question

此问题已经在这里有了答案：

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我具有以下Rust结构，其子结构具有HashMap。

use std::collections::HashMap;

#[derive(Debug)]
struct Node {
    children: HashMap<i32, Node>,
}

impl Node {
    fn no_children(&self) -> usize {
        if self.children.is_empty() {
            1
        } else {
            1 + self
                .children
                .into_iter()
                .map(|(_, child)| child.no_children())
                .sum::<usize>()
        }
    }
}

我实施了no_children(&self)以查找节点总数。但是，在self.children下，Rust突出显示了一个错误，因为：

error[E0507]: cannot move out of `self.children` which is behind a shared reference
  --> src/lib.rs:13:17
   |
13 |               1 + self
   |  _________________^
14 | |                 .children
   | |_________________________^ move occurs because `self.children` has type `std::collections::HashMap<i32, Node>`, which does not implement the `Copy` trait

我不确定缺少什么。我尝试添加&self.children...，但仍然遇到相同的错误。

Answer 1

[问题是.into_iter(self)需要拥有HashMap的所有权，但在no_immediate_children(&self)中，HashMap后面是引用->即&self而不是self；]]

您可以通过两种方式解决此问题，具体取决于要实现的目标：

1. 如果要使用哈希映射的元素，并在方法调用后将其保留为空：