Using #[derive(IntoIterator)]

• 1 Example usage
• 2 Structs
• 3 Enums

Deriving IntoIterator only works for a single field of a struct. The result is that you will call .into_iter() on this field directly.

With #[into_iterator] or #[into_iterator(ignore)] it’s possible to indicate the field that you want to derive IntoIterator for.

By using #[into_iterator(owned, ref, ref_mut)] it’s possible to derive an IntoIterator implementation for reference types as well. You can pick any combination of owned, ref and ref_mut. If that’s not provided the default is #[IntoIterator(owned)].

1 Example usage

#[derive(IntoIterator)]
struct MyVec(Vec<i32>);

// You can specify the field you want to derive IntoIterator for
#[derive(IntoIterator)]
struct Numbers {
    #[into_iterator(owned, ref,  ref_mut)]
    numbers: Vec<i32>,
    useless: bool,
}

fn main() {
    assert_eq!(Some(5), MyVec(vec![5, 8]).into_iter().next());

    let mut nums = Numbers{numbers: vec![100, 200], useless: false};
    assert_eq!(Some(&100), (&nums).into_iter().next());
    assert_eq!(Some(&mut 100), (&mut nums).into_iter().next());
    assert_eq!(Some(100), nums.into_iter().next());
}

2 Structs

When deriving IntoIterator for a struct:

#[derive(IntoIterator)]
struct Numbers {
    #[into_iterator(owned, ref,  ref_mut)]
    numbers: Vec<i32>,
    useless: bool,
}

Code like this will be generated:

impl ::core::iter::IntoIterator for Numbers {
    type Item = <Vec<i32> as ::core::iter::IntoIterator>::Item;
    type IntoIter = <Vec<i32> as ::core::iter::IntoIterator>::IntoIter;
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        <Vec<i32> as ::core::iter::IntoIterator>::into_iter(self.numbers)
    }
}

impl<'__deriveMoreLifetime> ::core::iter::IntoIterator for &'__deriveMoreLifetime Numbers {
    type Item = <&'__deriveMoreLifetime Vec<i32> as ::core::iter::IntoIterator>::Item;
    type IntoIter = <&'__deriveMoreLifetime Vec<i32> as ::core::iter::IntoIterator>::IntoIter;
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        <&'__deriveMoreLifetime Vec<i32> as ::core::iter::IntoIterator>::into_iter(&self.numbers)
    }
}

impl<'__deriveMoreLifetime> ::core::iter::IntoIterator for &'__deriveMoreLifetime mut Numbers {
    type Item = <&'__deriveMoreLifetime mut Vec<i32> as ::core::iter::IntoIterator>::Item;
    type IntoIter = <&'__deriveMoreLifetime mut Vec<i32> as ::core::iter::IntoIterator>::IntoIter;
    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        <&'__deriveMoreLifetime mut Vec<i32> as ::core::iter::IntoIterator>::into_iter(
            &mut self.numbers,
        )
    }
}

3 Enums

Deriving IntoIterator is not supported for enums.