Merge pull request #980 from Demonthos/improve-custom-hooks-docs

Improve the custom hooks chapter in the guide

docs/guide/Cargo.toml

@@ -16,12 +16,12 @@ dioxus-native-core-macro = { path = "../../packages/native-core-macro" }
 dioxus-router = { path = "../../packages/router" }
 dioxus-liveview = { path = "../../packages/liveview", features = ["axum"] }
 dioxus-tui = { path = "../../packages/dioxus-tui" }
-fermi = { path = "../../packages/fermi" }
-shipyard = "0.6.2"
-
 
 # dioxus = { path = "../../packages/dioxus", features = ["desktop", "web", "ssr", "router", "fermi", "tui"] }
+fermi = { path = "../../packages/fermi" }
+shipyard = "0.6.2"
 serde = { version = "1.0.138", features=["derive"] }
 reqwest = { version = "0.11.11", features = ["json"] }
 tokio = { version = "1.19.2" , features=[]}
 axum = { version = "0.6.1", features = ["ws"] }
+gloo-storage = "0.2.2"

docs/guide/examples/hooks_anti_patterns.rs

@@ -0,0 +1,38 @@
+#![allow(unused)]
+
+use dioxus::prelude::*;
+
+fn main() {}
+
+// ANCHOR: non_clone_state
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::sync::Arc;
+
+struct UseState<'a, T> {
+    value: &'a RefCell<T>,
+    update: Arc<dyn Fn()>,
+}
+
+fn my_use_state<T: 'static>(cx: &ScopeState, init: impl FnOnce() -> T) -> UseState<T> {
+    // The update function will trigger a re-render in the component cx is attached to
+    let update = cx.schedule_update();
+    // Create the initial state
+    let value = cx.use_hook(|| RefCell::new(init()));
+
+    UseState { value, update }
+}
+
+impl<T: Clone> UseState<'_, T> {
+    fn get(&self) -> T {
+        self.value.borrow().clone()
+    }
+
+    fn set(&self, value: T) {
+        // Update the state
+        *self.value.borrow_mut() = value;
+        // Trigger a re-render on the component the state is from
+        (self.update)();
+    }
+}
+// ANCHOR_END: non_clone_state

docs/guide/examples/hooks_composed.rs

@@ -11,3 +11,57 @@ fn use_settings(cx: &ScopeState) -> &UseSharedState<AppSettings> {
     use_shared_state::<AppSettings>(cx).expect("App settings not provided")
 }
 // ANCHOR_END: wrap_context
+
+// ANCHOR: use_storage
+use gloo_storage::{LocalStorage, Storage};
+use serde::{de::DeserializeOwned, Serialize};
+
+/// A persistent storage hook that can be used to store data across application reloads.
+#[allow(clippy::needless_return)]
+pub fn use_persistent<T: Serialize + DeserializeOwned + Default + 'static>(
+    cx: &ScopeState,
+    // A unique key for the storage entry
+    key: impl ToString,
+    // A function that returns the initial value if the storage entry is empty
+    init: impl FnOnce() -> T,
+) -> &UsePersistent<T> {
+    // Use the use_ref hook to create a mutable state for the storage entry
+    let state = use_ref(cx, move || {
+        // This closure will run when the hook is created
+        let key = key.to_string();
+        let value = LocalStorage::get(key.as_str()).ok().unwrap_or_else(init);
+        StorageEntry { key, value }
+    });
+
+    // Wrap the state in a new struct with a custom API
+    // Note: We use use_hook here so that this hook is easier to use in closures in the rsx. Any values with the same lifetime as the ScopeState can be used in the closure without cloning.
+    cx.use_hook(|| UsePersistent {
+        inner: state.clone(),
+    })
+}
+
+struct StorageEntry<T> {
+    key: String,
+    value: T,
+}
+
+/// Storage that persists across application reloads
+pub struct UsePersistent<T: 'static> {
+    inner: UseRef<StorageEntry<T>>,
+}
+
+impl<T: Serialize + DeserializeOwned + Clone + 'static> UsePersistent<T> {
+    /// Returns a reference to the value
+    pub fn get(&self) -> T {
+        self.inner.read().value.clone()
+    }
+
+    /// Sets the value
+    pub fn set(&self, value: T) {
+        let mut inner = self.inner.write();
+        // Write the new value to local storage
+        LocalStorage::set(inner.key.as_str(), &value);
+        inner.value = value;
+    }
+}
+// ANCHOR_END: use_storage

docs/guide/examples/hooks_custom_logic.rs

@@ -0,0 +1,57 @@
+#![allow(unused)]
+
+use dioxus::prelude::*;
+
+fn main() {}
+
+// ANCHOR: use_state
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::sync::Arc;
+
+#[derive(Clone)]
+struct UseState<T> {
+    value: Rc<RefCell<T>>,
+    update: Arc<dyn Fn()>,
+}
+
+fn my_use_state<T: 'static>(cx: &ScopeState, init: impl FnOnce() -> T) -> &UseState<T> {
+    cx.use_hook(|| {
+        // The update function will trigger a re-render in the component cx is attached to
+        let update = cx.schedule_update();
+        // Create the initial state
+        let value = Rc::new(RefCell::new(init()));
+
+        UseState { value, update }
+    })
+}
+
+impl<T: Clone> UseState<T> {
+    fn get(&self) -> T {
+        self.value.borrow().clone()
+    }
+
+    fn set(&self, value: T) {
+        // Update the state
+        *self.value.borrow_mut() = value;
+        // Trigger a re-render on the component the state is from
+        (self.update)();
+    }
+}
+// ANCHOR_END: use_state
+
+// ANCHOR: use_context
+pub fn use_context<T: 'static + Clone>(cx: &ScopeState) -> Option<&T> {
+    cx.use_hook(|| cx.consume_context::<T>()).as_ref()
+}
+
+pub fn use_context_provider<T: 'static + Clone>(cx: &ScopeState, f: impl FnOnce() -> T) -> &T {
+    cx.use_hook(|| {
+        let val = f();
+        // Provide the context state to the scope
+        cx.provide_context(val.clone());
+        val
+    })
+}
+
+// ANCHOR_END: use_context

docs/guide/src/en/interactivity/custom_hooks.md

@@ -2,6 +2,8 @@
 
 Hooks are a great way to encapsulate business logic. If none of the existing hooks work for your problem, you can write your own.
 
+When writing your hook, you can make a function that accepts `cx: &ScopeState` as a parameter to accept a scope with any Props.
+
 ## Composing Hooks
 
 To avoid repetition, you can encapsulate business logic based on existing hooks to create a new hook.
@@ -12,6 +14,12 @@ For example, if many components need to access an `AppSettings` struct, you can
 {{#include ../../../examples/hooks_composed.rs:wrap_context}}
 ```
 
+Or if you want to wrap a hook that persists reloads with the storage API, you can build on top of the use_ref hook to work with mutable state:
+
+```rust
+{{#include ../../../examples/hooks_composed.rs:use_storage}}
+```
+
 ## Custom Hook Logic
 
 You can use [`cx.use_hook`](https://docs.rs/dioxus/latest/dioxus/prelude/struct.ScopeState.html#method.use_hook) to build your own hooks. In fact, this is what all the standard hooks are built on!
@@ -23,4 +31,61 @@ You can use [`cx.use_hook`](https://docs.rs/dioxus/latest/dioxus/prelude/struct.
 Inside the initialization closure, you will typically make calls to other `cx` methods. For example:
 
 - The `use_state` hook tracks state in the hook value, and uses [`cx.schedule_update`](https://docs.rs/dioxus/latest/dioxus/prelude/struct.ScopeState.html#method.schedule_update) to make Dioxus re-render the component whenever it changes.
+
+Here is a simplified implementation of the `use_state` hook:
+
+```rust
+{{#include ../../../examples/hooks_custom_logic.rs:use_state}}
+```
+
 - The `use_context` hook calls [`cx.consume_context`](https://docs.rs/dioxus/latest/dioxus/prelude/struct.ScopeState.html#method.consume_context) (which would be expensive to call on every render) to get some context from the scope
+
+Here is an implementation of the `use_context` and `use_context_provider` hooks:
+
+```rust
+{{#include ../../../examples/hooks_custom_logic.rs:use_context}}
+```
+
+## Hook Anti-Patterns
+
+When writing a custom hook, you should avoid the following anti-patterns:
+
+- !Clone Hooks: To allow hooks to be used within async blocks, the hooks must be Clone. To make a hook clone, you can wrap data in Rc or Arc and avoid lifetimes in hooks.
+
+This version of use_state may seem more efficient, but it is not cloneable:
+
+```rust
+{{#include ../../../examples/hooks_anti_patterns.rs:non_clone_state}}
+```
+
+If we try to use this hook in an async block, we will get a compile error:
+
+```rust
+fn FutureComponent(cx: &ScopeState) -> Element {
+    let my_state = my_use_state(cx, || 0);
+    cx.spawn({
+        to_owned![my_state];
+        async move {
+            my_state.set(1);
+        }
+    });
+
+    todo!()
+}
+```
+
+But with the original version, we can use it in an async block:
+
+```rust
+fn FutureComponent(cx: &ScopeState) -> Element {
+    let my_state = use_state(cx, || 0);
+    cx.spawn({
+        to_owned![my_state];
+        async move {
+            my_state.set(1);
+        }
+    });
+
+    todo!()
+}
+```