Structs

Like tuples, Struct can also be destructured by matching:

struct Foo {
    x: (u32, u32),
    y: u32,
}

#[rustfmt::skip]
fn main() {
    let foo = Foo { x: (1, 2), y: 3 };
    match foo {
        Foo { y: 2, x: i }   => println!("y = 2, x = {i:?}"),
        Foo { x: (1, b), y } => println!("x.0 = 1, b = {b}, y = {y}"),
        Foo { y, .. }        => println!("y = {y}, other fields were ignored"),
    }
}
This slide should take about 4 minutes.
  • Change the literal values in foo to match with the other patterns.
  • Add a new field to Foo and make changes to the pattern as needed.

More to Explore

  • Try match &foo and check the type of captures. The pattern syntax remains the same, but the captures become shared references. This is match ergonomics and is often useful with match self when implementing methods on an enum.
    • The same effect occurs with match &mut foo: the captures become exclusive references.
  • The distinction between a capture and a constant expression can be hard to spot. Try changing the 2 in the second arm to a variable, and see that it subtly doesn’t work. Change it to a const and see it working again.