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docs: add important hooks
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.vscode/spellright.dict
vendored
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.vscode/spellright.dict
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@ -73,3 +73,6 @@ bootstrapper
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WebkitGtk
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laymans
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iter
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cloneable
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fudamental
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clonable
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@ -11,13 +11,130 @@ Both of these hooks are extremely powerful and flexible, so we've dedicated this
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If you're struggling with errors due to usage in hooks, make sure you're following the rules of hooks:
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- Functions with "use_" should not be called in callbacks
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- Functions with "use_" should not be called out of order
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- Functions with "use_" should not be called in loops or conditionals
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A large majority of issues that seem to be "wrong with Dioxus" are actually just a misuse of hooks.
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## `use_state`
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The `use_state` hook is very similar to its React counterpart.
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The `use_state` hook is very similar to its React counterpart. When we use it, we get two values:
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- The value itself as an `&T`
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- A handle to set the value `&UseState<T>`
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```rust
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let (count, set_count) = use_state(&cx, || 0);
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// then to set the count
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set_count(count + 1)
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```
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However, the `set_count` object is more powerful than it looks. You can use it as a closure, but you can also call methods on it to do more powerful operations.
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For instance, we can get a handle to the current value at any time:
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```rust
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let current: Rc<T> = set_count.current();
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```
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Or, we can get the inner handle to set the value
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```rust
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let setter: Rc<dyn Fn(T)> = set_count.setter();
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```
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Or, we can set a new value using the current value as a reference:
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```rust
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set_count.modify(|i| i + 1);
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```
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If the value is cheaply cloneable, then we can call `with_mut` to get a mutable reference to the value:
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```rust
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set_count.with_mut(|i| *i += 1);
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```
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Alternatively, we can call `make_mut` which gives us a `RefMut` to the underlying value:
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```rust
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*set_count.make_mut() += 1;
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```
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Plus, the `set_count` handle is cloneable into async contexts, so we can use it in futures.
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```rust
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// count up infinitely
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cx.spawn({
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to_owned![set_count];
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async move {
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loop {
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wait_ms(100).await;
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set_count.modify(|i| i + 1);
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}
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}
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})
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```
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## `use_ref`
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You might've noticed a fundamental limitation to `use_state`: to modify the value in-place, it must be cheaply cloneable. But what if your type is not cheap to clone?
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In these cases, you should reach for `use_ref` which is essentially just a glorified `Rc<RefCell<T>>` (typical Rust UI shenanigans).
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This provides us some runtime locks around our data, trading reliability for performance. For most cases though, you will find it hard to make `use_ref` crash.
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> Note: this is *not* exactly like its React counterpart since calling `write` will cause a re-render. For more React parity, use the `write_silent` method.
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To use the hook:
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```rust
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let names = use_ref(&cx, || vec!["susie", "calvin"]);
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```
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To read the hook values, use the `read()` method:
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```rust
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cx.render(rsx!{
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ul {
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names.read().iter().map(|name| {
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rsx!{ "{name}" }
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})
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}
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})
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```
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And then to write into the hook value, use the `write` method:
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```rust
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names.write().push("Tiger");
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```
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If you don't want to re-render the component when names is updated, then we can use the `write_silent` method:
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```rust
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names.write().push("Transmogrifier");
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```
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Again, like `UseState`, the `UseRef` handle is clonable into async contexts:
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```rust
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// infinitely push calvin into the list
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cx.spawn({
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to_owned![names];
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async move {
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loop {
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wait_ms(100).await;
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names.write().push("Calvin");
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}
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}
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})
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```
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## Wrapping up
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These two hooks are extremely powerful at storing state.
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