Create Adaptable Composable
Adaptable composables are reusable functions that can accept both reactive and non-reactive inputs. This allows developers to use the composable in a variety of contexts without worrying about the reactivity of the inputs.
Steps to design an adaptable composable in Vue.js:
- Confirm the composable's purpose and API design and expected inputs/outputs.
- Identify inputs params that should be reactive (MaybeRef / MaybeRefOrGetter).
- Use
toValue() or toRef() to normalize inputs inside reactive effects.
- Implement the core logic of the composable using Vue's reactivity APIs.
Core Type Concepts
Type Utilities
/**
* value or writable ref (value/ref/shallowRef/writable computed)
*/
export type MaybeRef<T = any> = T | Ref<T> | ShallowRef<T> | WritableComputedRef<T>;
/**
* MaybeRef<T> + ComputedRef<T> + () => T
*/
export type MaybeRefOrGetter<T = any> = MaybeRef<T> | ComputedRef<T> | (() => T);
Policy and Rules
- Read-only, computed-friendly input: use
MaybeRefOrGetter
- Needs to be writable / two-way input: use
MaybeRef
- Parameter might be a function value (callback/predicate/comparator): do not use
MaybeRefOrGetter, or you may accidentally invoke it as a getter.
- DOM/Element targets: if you want computed/derived targets, use
MaybeRefOrGetter.
When MaybeRefOrGetter or MaybeRef is used:
- resolve reactive value using
toRef() (e.g. watcher source)
- resolve non-reactive value using
toValue()
Examples
Adaptable useDocumentTitle Composable: read-only title parameter
import { watch, toRef } from 'vue'
import type { MaybeRefOrGetter } from 'vue'
export function useDocumentTitle(title: MaybeRefOrGetter<string>) {
watch(toRef(title), (t) => {
document.title = t
}, { immediate: true })
}
Adaptable useCounter Composable: two-way writable count parameter
import { watch, toRef } from 'vue'
import type { MaybeRef } from 'vue'
function useCounter(count: MaybeRef<number>) {
const countRef = toRef(count)
function add() {
countRef.value++
}
return { add }
}
