gpui-entity

// Create entity
let counter = cx.new(|cx| Counter { count: 0 });

// Read state
let count = counter.read(cx).count;

// Update state
counter.update(cx, |state, cx| {
    state.count += 1;
    cx.notify(); // Trigger re-render
});

// Weak reference (for closures/callbacks)
let weak = counter.downgrade();
let _ = weak.update(cx, |state, cx| {
    state.count += 1;
    cx.notify();
});

struct MyComponent {
    shared_state: Entity<SharedData>,
}

impl MyComponent {
    fn new(cx: &mut App) -> Entity<Self> {
        let shared = cx.new(|_| SharedData::default());

        cx.new(|cx| Self {
            shared_state: shared,
        })
    }

    fn update_shared(&mut self, cx: &mut Context<Self>) {
        self.shared_state.update(cx, |state, cx| {
            state.value = 42;
            cx.notify();
        });
    }
}

impl MyComponent {
    fn fetch_data(&mut self, cx: &mut Context<Self>) {
        let weak_self = cx.entity().downgrade();

        cx.spawn(async move |cx| {
            let data = fetch_from_api().await;

            // Update entity safely
            let _ = weak_self.update(cx, |state, cx| {
                state.data = Some(data);
                cx.notify();
            });
        }).detach();
    }
}

// ✅ Good: Weak reference prevents retain cycles
let weak = cx.entity().downgrade();
callback(move || {
    let _ = weak.update(cx, |state, cx| cx.notify());
});

// ❌ Bad: Strong reference may cause memory leak
let strong = cx.entity();
callback(move || {
    strong.update(cx, |state, cx| cx.notify());
});

// ✅ Good: Use inner cx from closure
entity.update(cx, |state, inner_cx| {
    inner_cx.notify(); // Correct
});

// ❌ Bad: Use outer cx (multiple borrow error)
entity.update(cx, |state, inner_cx| {
    cx.notify(); // Wrong!
});

// ✅ Good: Sequential updates
entity1.update(cx, |state, cx| { /* ... */ });
entity2.update(cx, |state, cx| { /* ... */ });

// ❌ Bad: Nested updates (may panic)
entity1.update(cx, |_, cx| {
    entity2.update(cx, |_, cx| { /* ... */ });
});