010 通過連結清單學習Rust之Iter

介紹

視訊位址：https://www.bilibili.com/video/av78062009/

相關源碼：https://github.com/anonymousGiga/Rust-link-list

詳細内容

Iter

//實作Iter
pub struct Iter<'a, T> {
  next: Option<&'a Node<T>>,
}

impl<T> List<T> {
  pub fn iter(&self) -> Iter<T> {
    Iter { next: self.head.as_deref() }
  }
}

impl<'a, T> Iterator for Iter<'a, T> {
  type Item = &'a T;
  fn next(&mut self) -> Option<Self::Item> {
    self.next.map(|node| {
      self.next = node.next.as_deref();
      &node.elem
    })
  }
}      

測試及完整代碼

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
        })
    }
}

//實作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()
    }
}

//實作Iter
pub struct Iter<'a, T> {
    next: Option<&'a Node<T>>,
}

impl<T> List<T> {
    pub fn iter(&self) -> Iter<T> {
        Iter { next: self.head.as_deref() }
    }
}

impl<'a, T> Iterator for Iter<'a, T> {
    type Item = &'a T;
    fn next(&mut self) -> Option<Self::Item> {
        self.next.map(|node| {
            self.next = node.next.as_deref();
            &node.elem
        })
    }
}
#[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| { //取指針
            //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);
    }

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

        let mut iter = list.iter(); 
        assert_eq!(iter.next(), Some(&3));
        assert_eq!(iter.next(), Some(&2));
        assert_eq!(iter.next(), Some(&1));
    }
}