介绍

视频地址：www.bilibili.com/video/av78062009/

相关源码：github.com/anonymousGiga/Rust-link...

详细内容

本节我们为链表实现迭代器。迭代器Trait的定义如下：

pub trait Iterator {
    type Item;
    fn next(&mut self) -> Option<Self::Item>;
}

对于我们来说，我们要实现以下三个迭代器：

IntoIter - T      //对应元素本身
IterMut - &mut T  //对应元素的可变引用
Iter - &T         //对应元素的引用

IntoIter

下面，我们先实现IntoIter如下：

//实现IntoIter
pub struct IntoIter<T>(List<T>);

impl<T> List<T> {
    pub fn into_iter(self) -> IntoIter<T> {IntoIter(self)}
}

impl<T> Iterator for IntoIter<T> {
    type Item = T;
    fn next(&mut self) -> Option<Self::Item> {
        self.0.pop()}
}

测试与完整代码

加上测试的完整代码：

pub struct List<T> {
    head: Link<T>,
}

type Link<T> = Option<Box<Node<T>>>;

struct Node<T> {
    elem: T,
    next: Link<T>,
}

impl<T> List<T> {
    pub fn new() -> Self {
        List { head: None }}

    pub fn push(&mut self, elem: T) {let node = Box::new(Node{
            elem: elem,
            next: self.head.take(),});
        self.head = Some(node);}

    pub fn pop(&mut self) -> Option<T> {
        self.head.take().map(|node| {
            self.head = node.next;
            node.elem
        })}

    pub fn peek(&self) -> Option<&T> {//self.head.map(|node| { 
        self.head.as_ref().map(|node| {&node.elem
        })}

    pub fn peek_mut(&mut self) -> Option<&mut T> {
        self.head.as_mut().map(|node| {&mut node.elem
        })}
}

//实现IntoIter
pub struct IntoIter<T>(List<T>);

impl<T> List<T> {
    pub fn into_iter(self) -> IntoIter<T> {IntoIter(self)}
}

impl<T> Iterator for IntoIter<T> {
    type Item = T;
    fn next(&mut self) -> Option<Self::Item> {
        self.0.pop()}
}

#[cfg(test)]
mod tests {
    use super::List;
    #[test] 
    fn basics() {let mut list = List::new();
        assert_eq!(list.pop(), None);

        list.push(1);
        list.push(2);
        list.push(3);

        assert_eq!(list.pop(), Some(3));
        assert_eq!(list.pop(), Some(2));

        list.push(4);
        list.push(5);

        assert_eq!(list.pop(), Some(5));
        assert_eq!(list.pop(), Some(4));

        assert_eq!(list.pop(), Some(1));
        assert_eq!(list.pop(), None);}

    #[test] 
    fn peek() {let mut list = List::new();

        assert_eq!(list.peek(), None);
        assert_eq!(list.peek_mut(), None);
        list.push(1); 
        list.push(2); 
        list.push(3);

        assert_eq!(list.peek(), Some(&3));
        assert_eq!(list.peek_mut(), Some(&mut 3));

        //list.peek_mut().map(|&mut value| {
        list.peek_mut().map(|value| { //取指针//value = 32*value = 32});

        assert_eq!(list.peek(), Some(&32));
        assert_eq!(list.pop(), Some(32));}

    #[test] 
    fn into_iter() {let mut list = List::new();
        list.push(1); 
        list.push(2); 
        list.push(3);

        let mut iter = list.into_iter();
        assert_eq!(iter.next(), Some(3));
        assert_eq!(iter.next(), Some(2));
        assert_eq!(iter.next(), Some(1));
        assert_eq!(iter.next(), None);}
}