mirror of https://github.com/yewstack/yew
52 lines
1.8 KiB
Plaintext
52 lines
1.8 KiB
Plaintext
---
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title: 'Hooks'
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slug: /concepts/function-components/hooks
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---
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## Hooks
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Hooks are functions that let you store state and perform side-effects.
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Yew comes with a few pre-defined Hooks. You can also create your own or discover many [community made hooks](/community/awesome#hooks).
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## Rules of hooks
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1. A hook function name always has to start with `use_`
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2. Hooks can only be used in the following locations:
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- Top level of a function / hook.
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- Blocks inside a function / hook, given it's not already branched.
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- In the condition of a top level `if` expression inside a function / hook.
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- In the scrutinee of a top level `match` expression inside a function / hook.
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3. Hooks must be called in the same order for every render. Returning early is only allowed when using [Suspense](../../suspense.mdx)
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These rules are enforced by either compile time or run-time errors.
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### Pre-defined Hooks
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Yew comes with the following predefined Hooks:
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- `use_state`
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- `use_state_eq`
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- `use_memo`
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- `use_callback`
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- `use_mut_ref`
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- `use_node_ref`
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- `use_reducer`
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- `use_reducer_eq`
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- `use_effect`
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- `use_effect_with_deps`
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- `use_context`
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- `use_force_update`
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The documentation for these hooks can be found in the [Yew API docs](https://yew-rs-api.web.app/next/yew/functional/)
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### Custom Hooks
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There are cases where you want to define your own Hooks to encapsulate potentially stateful logic from a component into reusable functions.
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See the [Defining custom hooks](concepts/function-components/hooks/custom-hooks.mdx#defining-custom-hooks) section for more information.
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## Further reading
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- The React documentation has a section on [React hooks](https://reactjs.org/docs/hooks-intro.html).
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These are not exactly the same as Yew's hooks, but the underlying concept is similar.
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