Queries

Queries allow finding individual Entities or collections of Entities. Best shown by examples:

struct Foo {
    // some fields
}

// find the first (presumably only) entity with some component Foo
let (entity, _) = hobo::find_one::<(Entity, With<Foo>)>();
let element = hobo::Element(entity);
element.set_text("This entity has Foo");

struct Frobnicator {
    num_fraculations: u32,
    // other fields
}

// find all entities with a Frobnicator component and mutate it
// perhaps as a result of some combined transformation
for frobnicator in hobo::find::<&mut Frobnicator>() {
    frobnicator.num_fraculations += 1;
}

Queries are tuples of & T, &mut T or With<T> where T is some component or, as a special case, Entity. The result of hobo::find (or hobo::find_one) are tuples where each member is what was requested by the query (With<T> will always return true in its position because any entity that doesn't have T won't be included in the output).

Queries are also often useful to establish relations with distant Elements. For example, an Element in one part of the DOM can get an Element from a completely unrelated part of the DOM.

use hobo::create as e;

struct SettingsData {
    speed: f32,
}

let settings_container = e::div()
    // etc
    .component(SettingsData { speed: 0.35 })

// -- snip --

let unrelated_display = e::div()
    //etc
    .text(hobo::find_one::<&SettingsData>().speed.to_string())