How to Use the Lending Iterator Pattern in Rust

Rust does not have a built-in 'Lending Iterator' pattern; instead, use the standard Iterator trait with references to borrow items without moving them. Implement the Iterator trait for your custom type and return &T (a reference) from the next method to allow borrowing elements from a collection.

struct MyIter<'a> {
    items: &'a [i32],
    index: usize,
}

impl<'a> Iterator for MyIter<'a> {
    type Item = &'a i32;

    fn next(&mut self) -> Option<Self::Item> {
        if self.index >= self.items.len() {
            return None;
        }
        let item = &self.items[self.index];
        self.index += 1;
        Some(item)
    }
}

fn main() {
    let data = vec![1, 2, 3];
    let mut iter = MyIter { items: &data, index: 0 };
    while let Some(&val) = iter.next() {
        println!("{}", val);
    }
}

The Lending Iterator Pattern in Rust lets you walk through a list of items and look at them one by one without taking ownership of the list or the items. It is like reading books from a library shelf: you can borrow a book to read it, but you don't take it home permanently. You use this when you need to process data that you cannot move or copy, such as large files or shared resources.