pub trait UseCallbackHook: UseMemoHook {
// Provided method
fn use_callback<F, R, D>(&self, factory: F, deps: D) -> Box<dyn Fn() -> R>
where R: 'static,
F: FnOnce() -> Box<dyn Fn() -> R>,
D: IntoIterator<Item: Dependency + Clone> { ... }
}Expand description
Trait for using callback hooks
This trait is automatically implemented for any type that implements HasHooks
(which includes all types using #[hook_element]).
Provided Methods§
Sourcefn use_callback<F, R, D>(&self, factory: F, deps: D) -> Box<dyn Fn() -> R>
fn use_callback<F, R, D>(&self, factory: F, deps: D) -> Box<dyn Fn() -> R>
Use a callback hook Returns a memoized function Note: deps parameter should be passed directly (array or tuple) to avoid temporary value lifetime issues The factory closure is passed first, followed by the dependencies array.
Examples found in repository?
examples/basic.rs (lines 43-52)
13 fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
14 // useState - 管理计数器状态
15 let (count, set_count) = self.use_state(|| 0i32);
16
17 // useMemo - 计算双倍值
18 let count_val = count();
19 let doubled = self.use_memo(|| count_val * 2, [count_val]);
20
21 // useEffect - 副作用，当count变化时执行
22 self.use_effect(
23 || {
24 println!("Effect: count changed to {}", count_val);
25 // 返回可选的清理函数
26 Some(|| {
27 println!("Effect cleanup: previous effect is being cleaned up");
28 })
29 },
30 [count_val],
31 );
32
33 // useRef - 创建一个可变引用，用于存储上一次的值
34 let prev_count_ref = self.use_ref(|| 0i32);
35 let current_count = count_val;
36
37 // 更新引用值
38 if current_count != *prev_count_ref.borrow() {
39 *prev_count_ref.borrow_mut() = current_count;
40 }
41
42 // useCallback - 创建一个记忆化的回调函数
43 let handle_increment = self.use_callback(
44 || {
45 let count_val = current_count;
46 Box::new(move || {
47 println!("Callback executed with count: {}", count_val);
48 count_val + 1
49 }) as Box<dyn Fn() -> i32>
50 },
51 [current_count],
52 );
53
54 div()
55 .flex()
56 .flex_col()
57 .gap_3()
58 .bg(rgb(0x2d2d2d))
59 .size(px(500.0))
60 .justify_center()
61 .items_center()
62 .shadow_lg()
63 .border_1()
64 .border_color(rgb(0x555555))
65 .text_xl()
66 .text_color(rgb(0xffffff))
67 // 计数器显示
68 .child(format!("Count: {}", count()))
69 // 双倍值显示（useMemo）
70 .child(format!("Doubled (useMemo): {}", doubled()))
71 // useRef显示
72 .child(format!(
73 "Previous count (useRef): {}",
74 *prev_count_ref.borrow()
75 ))
76 // 操作说明
77 .child("Check console for effect and callback logs")
78 .child(div().child("click me").id("counter").on_click(cx.listener(
79 move |_this, _, _window, cx| {
80 set_count(count() + 1);
81 cx.notify();
82 },
83 )))
84 // useCallback测试按钮
85 .child(
86 div()
87 .child("test callback")
88 .id("callback-test")
89 .on_click(cx.listener(move |_this, _, _window, _cx| {
90 let result = handle_increment();
91 println!("Callback returned: {}", result);
92 })),
93 )
94 }Dyn Compatibility§
This trait is not dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.