multi level sort in rust

multi-level-sort.rs

/// Multi-level sort a slice of Foobars according to [(field, reverse)]
fn sort_by_names(f: &mut [Foobar], orderings: &[(Foofields, bool)]) {
    use std::cmp::Ordering;
    
    f.sort_by(|a, b| {
        let mut cmp = Ordering::Equal;
        for (field, reverse) in orderings {
            if cmp != Ordering::Equal {
                break;
            }
            cmp = match *field {
                Foofields::Foo => a.foo.cmp(&b.foo),
                Foofields::Bar => a.bar.cmp(&b.bar),
                Foofields::Oof => a.oof.cmp(&b.oof),
            };
            cmp = if *reverse { cmp.reverse() } else { cmp };
        }
        cmp
    })
}

/// An arbitrary struct
#[derive(Debug)]
struct Foobar {
    foo: i32,
    bar: i32,
    oof: &'static str,
}

/// Typesafe enumeration of fields on `Foobar`
enum Foofields {
    Foo,
    Bar,
    Oof,
}

fn main() {
    let mut f = vec![
        Foobar {
            foo: 3,
            bar: 1,
            oof: "B",
        },
        Foobar {
            foo: 1,
            bar: 2,
            oof: "B",
        },
        Foobar {
            foo: 2,
            bar: 2,
            oof: "A",
        },
    ];

    //  Apply sorts in reverse order.
    sort_by_names(&mut f, &[( Foofields::Bar, false), (Foofields::Oof, false)]);

    println!("{:?}", &f);
}