77 lines
1.7 KiB
Rust
77 lines
1.7 KiB
Rust
use std::rc::Rc;
|
|
|
|
use dioxus_core::prelude::*;
|
|
|
|
/// Store constant state between component renders.
|
|
///
|
|
/// UseConst allows you to store state that is initialized once and then remains constant across renders.
|
|
/// You can only get an immutable reference after initalization.
|
|
/// This can be useful for values that don't need to update reactively, thus can be memoized easily
|
|
///
|
|
/// ```rust, ignore
|
|
/// struct ComplexData(i32);
|
|
///
|
|
/// fn Component(cx: Scope) -> Element {
|
|
/// let id = use_const(cx, || ComplexData(100));
|
|
///
|
|
/// cx.render(rsx! {
|
|
/// div { "{id.0}" }
|
|
/// })
|
|
/// }
|
|
/// ```
|
|
#[must_use]
|
|
pub fn use_const<T: 'static>(
|
|
cx: &ScopeState,
|
|
initial_state_fn: impl FnOnce() -> T,
|
|
) -> &UseConst<T> {
|
|
cx.use_hook(|| UseConst {
|
|
value: Rc::new(initial_state_fn()),
|
|
})
|
|
}
|
|
|
|
#[derive(Clone)]
|
|
pub struct UseConst<T> {
|
|
value: Rc<T>,
|
|
}
|
|
|
|
impl<T> PartialEq for UseConst<T> {
|
|
fn eq(&self, other: &Self) -> bool {
|
|
Rc::ptr_eq(&self.value, &other.value)
|
|
}
|
|
}
|
|
|
|
impl<T: core::fmt::Display> core::fmt::Display for UseConst<T> {
|
|
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
|
|
self.value.fmt(f)
|
|
}
|
|
}
|
|
|
|
impl<T> UseConst<T> {
|
|
pub fn get_rc(&self) -> &Rc<T> {
|
|
&self.value
|
|
}
|
|
}
|
|
|
|
impl<T> std::ops::Deref for UseConst<T> {
|
|
type Target = T;
|
|
|
|
fn deref(&self) -> &Self::Target {
|
|
self.value.as_ref()
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn use_const_makes_sense() {
|
|
#[allow(unused)]
|
|
|
|
fn app(cx: Scope) -> Element {
|
|
let const_val = use_const(cx, || vec![0, 1, 2, 3]);
|
|
|
|
assert!(const_val[0] == 0);
|
|
|
|
// const_val.remove(0); // Cannot Compile, cannot get mutable reference now
|
|
|
|
None
|
|
}
|
|
}
|