65 lines
1.5 KiB
Markdown
65 lines
1.5 KiB
Markdown
---
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title: State Management
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slug: /state
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---
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OSUI has builtin state management, the `State<T>` type is easy to use. A `State<T>` makes dependencies reload if the state is updated.
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## Example
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A counter app that increments every 100 milliseconds
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```rust src/main.rs
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use osui::prelude::*;
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fn main() -> std::io::Result<()> {
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let screen = Screen::new();
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let count = use_state(0);
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rsx! {
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%count // Dependency of count
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"Count: {count}"
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}
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.draw(&screen);
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std::thread::spawn(move || loop {
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**count.get() += 1;
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std::thread::sleep(std::time::Duration::from_millis(100));
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});
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screen.run()
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}
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```
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## `use_state<T>(v: T) -> State<T>`
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Returns a State of T with the specified default value.
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## `State<T>`
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A smart pointer that is wrapped around a `Arc<Mutex<T>>` and manages the state of the holding value, any changes will result in the dependencies reloading, making a smart and efficient approach instead of reloading the whole thing.
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### `get(&self) -> MutexGuard<'_, Inner<T>>`
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Gets a lock on the state for read/write access.
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### `set(&self, v: T)`
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Sets the value and marks it as updated.
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### `update(&self)`
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Marks the state as updated.
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## Trait `DependencyHandler`
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The `DependencyHandler` trait is a state management trait that will reload dependencies if the values are true
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### `fn add(&self)`
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Called when a dependency is added, for incrementing a dependency counter.
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### `check(&self) -> bool`
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Should return if the dependencies need to reload, if `true` the dependencies will reload, called after render.
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