mirror of https://github.com/yewstack/yew
89 lines
2.9 KiB
Plaintext
89 lines
2.9 KiB
Plaintext
---
|
|
title: "Custom Hooks"
|
|
description: "Defining your own Hooks "
|
|
---
|
|
|
|
## Defining custom Hooks
|
|
|
|
Component's stateful logic can be extracted into usable function by creating custom Hooks.
|
|
|
|
Consider that we have a component which subscribes to an agent and displays the messages sent to it.
|
|
```rust
|
|
use yew::{function_component, html, use_effect, use_state, Callback};
|
|
use yew_agent::Bridged;
|
|
// EventBus is an implementation yew_agent::Agent
|
|
use website_test::agents::EventBus;
|
|
|
|
|
|
#[function_component(ShowMessages)]
|
|
pub fn show_messages() -> Html {
|
|
let state = use_state(Vec::new);
|
|
|
|
{
|
|
let state = state.clone();
|
|
use_effect(move || {
|
|
let producer = EventBus::bridge(Callback::from(move |msg| {
|
|
let mut messages = (*state).clone();
|
|
messages.push(msg);
|
|
state.set(messages)
|
|
}));
|
|
|
|
|| drop(producer)
|
|
});
|
|
}
|
|
|
|
let output = state.iter().map(|it| html! { <p>{ it }</p> });
|
|
html! { <div>{ for output }</div> }
|
|
}
|
|
```
|
|
|
|
There's one problem with this code: the logic can't be reused by another component.
|
|
If we build another component which keeps track of the messages, instead of copying the code we can move the logic into a custom hook.
|
|
|
|
We'll start by creating a new function called `use_subscribe`.
|
|
The `use_` prefix conventionally denotes that a function is a hook.
|
|
This function will take no arguments and return `Rc<RefCell<Vec<String>>>`.
|
|
```rust
|
|
use std::{cell::RefCell, rc::Rc};
|
|
|
|
fn use_subscribe() -> Rc<RefCell<Vec<String>>> {
|
|
todo!()
|
|
}
|
|
```
|
|
|
|
This is a simple hook which can be created by combining other hooks. For this example, we'll two pre-defined hooks.
|
|
We'll use `use_state` hook to store the `Vec` for messages, so they persist between component re-renders.
|
|
We'll also use `use_effect` to subscribe to the `EventBus` `Agent` so the subscription can be tied to component's lifecycle.
|
|
|
|
```rust
|
|
use std::collections::HashSet;
|
|
use yew::{use_effect, use_state, Callback};
|
|
use yew_agent::Bridged;
|
|
// EventBus is an implementation yew_agent::Agent
|
|
use website_test::agents::EventBus;
|
|
|
|
fn use_subscribe() -> Vec<String> {
|
|
let state = use_state(Vec::new);
|
|
|
|
let effect_state = state.clone();
|
|
|
|
use_effect(move || {
|
|
let producer = EventBus::bridge(Callback::from(move |msg| {
|
|
let mut messages = (*effect_state).clone();
|
|
messages.push(msg);
|
|
effect_state.set(messages)
|
|
}));
|
|
|| drop(producer)
|
|
});
|
|
|
|
(*state).clone()
|
|
}
|
|
```
|
|
|
|
Although this approach works in almost all cases, it can't be used to write primitive hooks like the pre-defined hooks we've been using already
|
|
|
|
### Writing primitive hooks
|
|
|
|
`use_hook` function is used to write such hooks. View the docs on [docs.rs](https://docs.rs/yew/0.18.0/yew-functional/use_hook.html) for the documentation
|
|
and `hooks` directory to see implementations of pre-defined hooks.
|