Advanced Pattern Matching

If Case

released Fri, 15 Feb 2019
Swift Version 5.0

Using if case

if case can be used as the opposite of guard case. It is a great way to unwrap and match data within a branch. In line with our previous guard example. Obviously, we need an move function. Something that allows us to say that an entity moved in a direction. Since our entities are enums, we need to return an updated entity.

func move(entity: Entity, xd: Int, yd: Int) -> Entity {
    if case Entity.Entry(let t, let x, let y, let hp) = entity
    where (x + xd) < 1000 &&
        (y + yd) < 1000 {
    return Entity.Entry(type: t, x: (x + xd), y: (y + yd), hp: hp)
    return entity
print(move(Entity.Entry(type: .soldier, x: 10, y: 10, hp: 79), xd: 30, yd: 500))
// prints: Entry(main.Entity.EntityType.soldier, 40, 510, 79)