add optional dependency variants of selectors and effects

packages/signals/src/selector.rs

@@ -1,5 +1,7 @@
 use dioxus_core::prelude::*;
 
+use crate::dependency::Dependency;
+use crate::use_signal;
 use crate::{get_effect_stack, signal::SignalData, CopyValue, Effect, ReadOnlySignal, Signal};
 
 /// Creates a new Selector. The selector will be run immediately and whenever any signal it reads changes.
@@ -26,6 +28,44 @@ pub fn use_selector<R: PartialEq>(
     *cx.use_hook(|| selector(f))
 }
 
+/// Creates a new Selector with some local dependencies. The selector will be run immediately and whenever any signal it reads or any dependencies it tracks changes
+///
+/// Selectors can be used to efficiently compute derived data from signals.
+///
+/// ```rust
+/// use dioxus::prelude::*;
+/// use dioxus_signals::*;
+///
+/// fn App(cx: Scope) -> Element {
+///     let mut local_state = use_state(cx, || 0);
+///     let double = use_selector_with_dependencies(cx, (local_state.get(),), move |(local_state,)| local_state * 2);
+///     local_state.set(1);
+///  
+///     render! { "{double}" }
+/// }
+/// ```
+pub fn use_selector_with_dependencies<R: PartialEq, D: Dependency>(
+    cx: &ScopeState,
+    dependencies: D,
+    mut f: impl FnMut(D::Out) -> R + 'static,
+) -> ReadOnlySignal<R>
+where
+    D::Out: 'static,
+{
+    let dependencies_signal = use_signal(cx, || dependencies.out());
+    let selector = *cx.use_hook(|| {
+        selector(move || {
+            let deref = &*dependencies_signal.read();
+            f(deref.clone())
+        })
+    });
+    let changed = { dependencies.changed(&*dependencies_signal.read()) };
+    if changed {
+        dependencies_signal.set(dependencies.out());
+    }
+    selector
+}
+
 /// Creates a new Selector. The selector will be run immediately and whenever any signal it reads changes.
 ///
 /// Selectors can be used to efficiently compute derived data from signals.