Iterators

Iteration is one of the most important features of an ECS.

In Shipyard this is achieved using IntoIter::iter on views.

let world = World::new();

let (mut u32s, usizes) = world.borrow::<(ViewMut<u32>, View<usize>)>().unwrap();

for i in u32s.iter() {
    dbg!(i);
}

for (mut i, j) in (&mut u32s, &usizes).iter() {
    *i += *j as u32;
}

You can use views in any order. However, using the same combination of views in different positions might yield components in a different order.
You shouldn't expect specific ordering from Shipyard's iterators in general.

With Id

You can ask an iterator to tell you which entity owns each component by using WithId::with_id:

let world = World::new();

let u32s = world.borrow::<View<u32>>().unwrap();

for (id, i) in u32s.iter().with_id() {
    println!("{} belongs to entity {:?}", i, id);
}

Not

It's possible to filter entities that don't have a certain component using Not by adding ! in front of the view reference.

let world = World::new();

let (u32s, usizes) = world.borrow::<(View<u32>, View<usize>)>().unwrap();

for (i, _) in (&u32s, !&usizes).iter() {
    dbg!(i);
}