---
title: 'use_state'
---

`use_state` is used to manage state in a function component.
It returns a `UseStateHandle` object which `Deref`s to the currently stored value
and provides a `set` method to update the value.

The hook takes a function as input which determines the initial value.

:::tip Advanced tip

The setter function is guaranteed to be the same across the entire
component lifecycle. You can safely omit the `UseStateHandle` from the
dependents of `use_effect_with_deps` if you only intend to set
values from within the hook.

:::

This hook will always trigger a re-render upon receiving a new state. See
[`use_state_eq`](#use_state_eq) if you want the component to only
re-render when the new state compares unequal to the existing one.

## Example

```rust
use std::ops::Deref;
use yew::{Callback, function_component, html, use_state, Html};

#[function_component]
fn StateExample() -> Html {
    let name_handle = use_state(|| String::from("Bob"));
    let name = name_handle.deref().clone();
    let onclick = {
        let name = name.clone();
        Callback::from(move |_| name_handle.set(format!("{}y Jr.", name)))
    };


    html! {
        <div>
            <button {onclick}>{ "Update name" }</button>
            <p>
                <b>{ "My name is: " }</b>
                { name }
            </p>
        </div>
    }
}
```

:::caution

The value held in the handle will reflect the value at the time the
handle is returned by the `use_state`. It is possible that the handle
does not dereference to an up to date value if you are moving it into a
`use_effect_with_deps` hook. You can register the
state to the dependents so the hook can be updated when the value changes.

:::

## `use_state_eq`

This hook has the same effect as `use_state` but will only trigger a
re-render when the setter receives a value that `prev_state != next_state`.

This hook requires the state object to implement `PartialEq`.
