View-Model usage test

test_view_model.rs

const FOO_VIEW_MODEL: &str = "foo";
const COUNTER_PROPERTY: &str = "counter";
const FLAG_PROPERTY: &str = "flag";

// view-model data type
struct Foo {
    // can hold view-model value wrapper that implicitly notifies on mutation.
    counter: ViewModelValue<usize>,
    // or can hold raw notifiers to explicitly notify.
    flag: bool,
    flag_notifier: ViewModelNotifier,
}

impl Foo {
    fn toggle(&mut self) {
        self.flag = !self.flag;
        self.flag_notifier.notify();
    }
}

#[test]
fn test_view_model() {
    let a = WidgetId::from_str("a:root/a").unwrap();
    let b = WidgetId::from_str("b:root/b").unwrap();
    let mut collection = ViewModelCollection::default();

    // create new view-model and add it to collection.
    // `produce` method allows to setup notifiers as we construct view-model.
    let mut view_model = ViewModel::produce(|properties| Foo {
        counter: ViewModelValue::new(0, properties.notifier(COUNTER_PROPERTY)),
        flag: false,
        flag_notifier: properties.notifier(FLAG_PROPERTY),
    });
    // handle to view-model data we can use to share around.
    // it stays alive as long as its view-model object.
    let mut handle = view_model.lazy::<Foo>().unwrap();
    collection.insert(FOO_VIEW_MODEL.to_owned(), view_model);

    // unbound properties won't trigger notification until we bind widgets to them.
    assert_eq!(collection.consume_notified_common_root().is_valid(), false);
    handle.write().unwrap().toggle();
    assert_eq!(collection.consume_notified_common_root().is_valid(), false);
    assert!(collection
        .get_mut(FOO_VIEW_MODEL)
        .unwrap()
        .properties
        .bindings(COUNTER_PROPERTY)
        .unwrap()
        .is_notified());
    assert!(collection
        .get_mut(FOO_VIEW_MODEL)
        .unwrap()
        .properties
        .bindings(FLAG_PROPERTY)
        .unwrap()
        .is_notified());

    // bind widget to properties.
    // whenever property gets notified, its widgets will rebuild.
    collection
        .get_mut(FOO_VIEW_MODEL)
        .unwrap()
        .properties
        .bindings(COUNTER_PROPERTY)
        .unwrap()
        .bind(a);
    collection
        .get_mut(FOO_VIEW_MODEL)
        .unwrap()
        .properties
        .bindings(FLAG_PROPERTY)
        .unwrap()
        .bind(b);

    // once we bind properties, notification will be triggered.
    assert_eq!(
        collection.consume_notified_common_root().path(),
        Some("root")
    );

    // automatically notify on view-model value mutation.
    *handle.write().unwrap().counter += 1;
    assert_eq!(
        collection.consume_notified_common_root().path(),
        Some("root/a"),
    );

    // proxy notify via view-model method call.
    handle.write().unwrap().toggle();
    assert_eq!(
        collection.consume_notified_common_root().path(),
        Some("root/b"),
    );

    // rebuilding widgets tree will occur always from common root of notified widgets.
    *handle.write().unwrap().counter += 1;
    handle.write().unwrap().toggle();
    assert_eq!(
        collection.consume_notified_common_root().path(),
        Some("root"),
    );
}