75 lines
2.2 KiB
Markdown
75 lines
2.2 KiB
Markdown
---
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category: Reactivity
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---
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# toRef
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Normalize value/ref/getter to `ref` or `computed`.
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## Usage
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```ts
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import { toRef } from '@vueuse/core'
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const foo = ref('hi')
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const a = toRef(0) // Ref<number>
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const b = toRef(foo) // Ref<string>
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const c = toRef(() => 'hi') // ComputedRef<string>
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```
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## Differences from Vue's `toRef`
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VueUse's `toRef` is not the same as Vue’s `toRef` from the `vue` package.
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### VueUse `toRef`
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- Accepts **value**, **ref**, or **getter**
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- Returns:
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- a **ref** for primitive values
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- a **ref** for existing refs
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- a **computed** for getter functions
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- Does **not** accept `object + key`
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- Getters always produce readonly computed values
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### Vue `toRef`
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- Accepts only:
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- a **reactive object + property key**, or
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- an existing **ref**
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- Produces a **writable ref** linked to the underlying reactive object
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- Does **not** accept primitive values
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- Does **not** accept getter functions
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### Summary
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| Behavior | VueUse `toRef` | Vue `toRef` |
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| ------------------------ | ------------------------- | ----------------------- |
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| Accepts primitive values | ✔️ | ❌ |
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| Accepts getter | ✔️ (computed) | ❌ |
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| Accepts existing ref | ✔️ | ✔️ |
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| Accepts object + key | ❌ | ✔️ |
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| Writable | ✔️ (except getter) | ✔️ |
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| Purpose | Normalize to ref/computed | Bind to reactive object |
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## Type Declarations
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```ts
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/**
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* Normalize value/ref/getter to `ref` or `computed`.
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*/
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export declare function toRef<T>(r: () => T): Readonly<Ref<T>>
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export declare function toRef<T>(r: ComputedRef<T>): ComputedRef<T>
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export declare function toRef<T>(r: MaybeRefOrGetter<T>): Ref<T>
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export declare function toRef<T>(r: T): Ref<T>
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export declare function toRef<T extends object, K extends keyof T>(
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object: T,
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key: K,
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): ToRef<T[K]>
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export declare function toRef<T extends object, K extends keyof T>(
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object: T,
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key: K,
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defaultValue: T[K],
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): ToRef<Exclude<T[K], undefined>>
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```
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