## Additional Information that may be useful
This function is a hook which means you need to follow the rules of hooks when you call it. You can click here to learn more about the rules of hooks. Hooks in dioxus need to run in the same order every time you run the component. To make sure you run hooks in a consistent order, you should follow the rules of hooks: 1. Hooks should only be called from the root of a component or another hook ```rust # use dioxus::prelude::*; fn App() -> Element { // ✅ You can call hooks from the body of a component let number = use_signal(|| 1); if number() == 1 { // ❌ You can run into issues if you can hooks inside other expressions inside your component // If number changes from 0 to 1, the order of the hooks will be different and your app may panic let string = use_signal(|| "hello world".to_string()); } todo!() } fn use_my_hook() -> Signal { // ✅ You can call hooks from the body of other hooks let number = use_signal(|| 1); // ❌ Again, creating hooks inside expressions inside other hooks can cause issues if number() == 1 { let string = use_signal(|| "hello world".to_string()); } number } ``` 2. Hooks should always start with `use_` to make it clear that you need to call them in a consistent order Because hooks should only be called from the root of a component or another hook, you shouldn't call hooks inside of: - ❌ Conditionals ```rust # use dioxus::prelude::*; fn App() -> Element { let number = use_signal(|| 1); // ❌ Changing the condition will change the order of the hooks if number() == 1 { let string = use_signal(|| "hello world".to_string()); } // ❌ Changing the value you are matching will change the order of the hooks match number() { 1 => { let string = use_signal(|| "hello world".to_string()); }, _ => (), } todo!() } ``` - ❌ Loops ```rust # use dioxus::prelude::*; fn App() -> Element { let number = use_signal(|| 1); // ❌ Changing the loop will change the order of the hooks for i in 0..number() { let string = use_signal(|| "hello world".to_string()); } todo!() } ``` - ❌ Event Handlers ```rust # use dioxus::prelude::*; fn App() -> Element { rsx! { button { onclick: move |_| { // ❌ Calling the event handler will change the order of the hooks use_signal(|| "hello world".to_string()); }, "Click me" } } } ``` - ❌ Initialization closures in other hooks ```rust # use dioxus::prelude::*; fn App() -> Element { let number = use_signal(|| { // ❌ This closure will only be called when the component is first created. Running the component will change the order of the hooks let string = use_signal(|| "hello world".to_string()); string() }); todo!() } ```
Why do hooks need to run in a consistent order? Hooks need to be run in a consistent order because dioxus stores hooks in a list and uses the order you run hooks in to determine what part of the state belongs to which hook. Lets look at an example component: ```rust # use dioxus::prelude::*; fn App() -> Element { let number = use_signal(|| 1); // Hook 1 let string = use_signal(|| "hello world".to_string()); // Hook 2 let doubled = use_memo(move || number() * 2); // Hook 3 todo!() } ``` When we first create the component, we run the hooks in the order they are defined and store the state in the component in a list. ```rust, ignore [ Box::new(1), Box::new("hello world".to_string()), Box::new(2), ] ``` Next time we run the component, we return items from the state list instead of creating state again. ```rust, ignore [ Box::new(1), // Hook 1 returns 1 Box::new("hello world".to_string()), // Hook 2 returns "hello world" Box::new(2), // Hook 3 returns 2 ] ``` The order the hooks are run it must be the same because the order determines which hook gets what state! If you run the hooks in a different order, dioxus may panic because it can't turn the state back into the right type or you may just get the wrong state for your hook.