错误:无法移出自助领域的借用内容

Question

这是我的代码:

struct Node<T> {
    data: T,
    next: Option<Box<Node<T>>>,
}

impl<T> Node<T> {
    fn new(data : T) -> Node<T> {
        Node { data: data, next: None } 
    }
    fn new_with_next(data: T, next: Option<Box<Node<T>>>) -> Node<T> {
        Node { data: data, next: next }
    }
}


struct LinkedList<T> {
    head: Box<Node<T>>,
    size: u8,
}

impl<T> LinkedList<T> {
    fn new(data: T) -> LinkedList<T> {
        let new_node = Node::new(data);
        let head = Box::new(new_node);
        LinkedList { head: head, size: 1 }
    }
    fn insert(&mut self, data: T) {
        let mut next = Some(self.head);    // <-- error here
        let new_node = Node::new_with_next(data, next);
        self.head = Box::new(new_node);
        self.size += 1;
    }
}

我收到此错误:

src\linked_list.rs:28:29: 28:33 error: cannot move out of borrowed content [E0507]
src\linked_list.rs:28         let next = Some(self.head);
                                              ^~~~

我不明白错误,也不了解如何修复错误.我试图给一个参考self.head来Some,但我改变了数据类型这里面Some这种方式.

Answer 1

问题是你self通过引用,因此你不能移出它head(它将变得无效),这let mut next = Some(self.head);将做.

std::mem::replace 这是一个很好的功能:

fn insert(&mut self, data: T) {
    let mut next = std::mem::replace(&mut self.head, Box::new(Node::new(data)));
    self.head.next = Some(next);
    self.size += 1;
}

它可以让你用一个新节点替换头,并得到旧的同时,这锈是高兴,因为head保持有效,一直以来现.