use TearDown bound instead of FnOnce() for effect hooks

Fixes #61. Replaces the old `Destructor: FnOnce() + 'static` bound with
`Destructor: TearDown` on use_effect_once, use_effect_update, and
use_effect_update_with_deps, so users no longer need to return `|| ()`
when there is no cleanup logic.

Author: Madoshakalaka

crates/yew-hooks/src/hooks/use_effect_once.rs

@@ -28,7 +28,7 @@ use yew::prelude::*;
 pub fn use_effect_once<Callback, Destructor>(callback: Callback)
 where
     Callback: FnOnce() -> Destructor + 'static,
-    Destructor: FnOnce() + 'static,
+    Destructor: TearDown,
 {
     use_effect_with((), move |_| callback());
 }

crates/yew-hooks/src/hooks/use_effect_update.rs

@@ -17,8 +17,6 @@ use super::use_is_first_mount;
 /// fn effect_update() -> Html {
 ///     use_effect_update(|| {
 ///         debug!("Running effect only on updates");
-///
-///         || ()
 ///     });
 ///     
 ///     html! {
@@ -31,15 +29,16 @@ use super::use_is_first_mount;
 pub fn use_effect_update<Callback, Destructor>(callback: Callback)
 where
     Callback: FnOnce() -> Destructor + 'static,
-    Destructor: FnOnce() + 'static,
+    Destructor: TearDown,
 {
     let first = use_is_first_mount();
 
     use_effect(move || {
         if first {
             Box::new(|| ()) as Box<dyn FnOnce()>
         } else {
-            Box::new(callback())
+            let d = callback();
+            Box::new(move || d.tear_down())
         }
     });
 }
@@ -52,7 +51,7 @@ pub fn use_effect_update_with_deps<Callback, Destructor, Dependents>(
     deps: Dependents,
 ) where
     Callback: FnOnce(&Dependents) -> Destructor + 'static,
-    Destructor: FnOnce() + 'static,
+    Destructor: TearDown,
     Dependents: PartialEq + 'static,
 {
     let first = use_is_first_mount();
@@ -61,7 +60,8 @@ pub fn use_effect_update_with_deps<Callback, Destructor, Dependents>(
         if first {
             Box::new(|| ()) as Box<dyn FnOnce()>
         } else {
-            Box::new(callback(deps))
+            let d = callback(deps);
+            Box::new(move || d.tear_down())
         }
     });
 }

examples/yew-app/src/app/hooks/use_effect_update.rs

@@ -14,7 +14,6 @@ pub fn UseEffectUpdate() -> Html {
         let count_effect = count_effect.clone();
         use_effect_with(count.clone(), move |_| {
             count_effect.set(*count_effect + 1);
-            || ()
         });
     }
 
@@ -25,7 +24,6 @@ pub fn UseEffectUpdate() -> Html {
         use_effect_update_with_deps(
             move |_| {
                 count_effect_update.set(*count_effect_update + 1);
-                || ()
             },
             count,
         );