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use std::ops::Deref;
use std::rc::Rc;
use yew::prelude::*;
/// State handle for the [`use_previous`] hook.
pub struct UsePreviousHandle<T> {
inner: Rc<T>,
}
impl<T> UsePreviousHandle<T> {
/// Get the previous immutable ref to state or props.
pub fn previous(&self) -> Rc<T> {
self.inner.clone()
}
}
impl<T> Deref for UsePreviousHandle<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.inner
}
}
impl<T> Clone for UsePreviousHandle<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
}
}
}
impl<T> PartialEq for UsePreviousHandle<T>
where
T: PartialEq,
{
fn eq(&self, other: &Self) -> bool {
*self.inner == *other.inner
}
}
/// This hook returns the previous immutable ref to state or props.
///
/// # Example
///
/// ```rust
/// # use yew::prelude::*;
/// #
/// use yew_hooks::prelude::*;
///
/// #[function_component(UsePrevious)]
/// fn previous() -> Html {
/// let state = use_state(|| 0);
/// let previous_state = use_previous(state.clone());
///
///
/// let onincrease = {
/// let state = state.clone();
/// Callback::from(move |_| state.set(*state + 1))
/// };
/// let ondecrease = {
/// let state = state.clone();
/// Callback::from(move |_| state.set(*state - 1))
/// };
///
/// html! {
/// <div>
/// <button onclick={onincrease}>{ "Increase" }</button>
/// <button onclick={ondecrease}>{ "Decrease" }</button>
/// <p>
/// <b>{ "Current value: " }</b>
/// { *state }
/// </p>
/// <p>
/// <b>{ "Previous value: " }</b>
/// { **previous_state }
/// </p>
/// </div>
/// }
/// }
/// ```
#[hook]
pub fn use_previous<T>(value: T) -> UsePreviousHandle<T>
where
T: 'static,
{
let value_rc = Rc::new(value);
let state = use_mut_ref(|| value_rc.clone());
// Update the ref each render so if it changes the newest value will be saved.
let inner = state.replace(value_rc);
UsePreviousHandle { inner }
}