useRegistry

A foundational composable for building registration-based systems, managing collections of registered items with automatic indexing, and lifecycle management.

Usage

The useRegistry composable provides a powerful interface for managing collections of items in a registration-based system. It allows you to register, unregister, and look up items efficiently, while maintaining an index for quick access.

import { useRegistry } from '@vuetify/v0'

const registry = useRegistry()

const ticket1 = registry.register()
const ticket2 = registry.register()
const ticket3 = registry.register()

console.log(registry.size) // 3

API

• Type

  interface RegistryTicket {
    id: ID
    index: number
    value: unknown
    valueIsIndex: boolean
  }
  
  interface RegistryContext<Z extends RegistryTicket = RegistryTicket> {
    collection: Map<ID, Z>
    clear: () => void
    has: (id: ID) => boolean
    keys: () => ID[]
    browse: (value: unknown) => ID | ID[] | undefined
    lookup: (index: number) => ID | undefined
    get: (id: ID) => Z | undefined
    upsert: (id: ID, patch?: Partial<Z>) => Z
    values: () => Z[]
    entries: () => [ID, Z][]
    register: (item?: Partial<Z>) => Z
    unregister: (id: ID) => void
    reindex: () => void
    seek: (direction?: 'first' | 'last', from?: number, predicate?: (ticket: Z) => boolean) => Z | undefined
    on: (event: string, cb: Function) => void
    off: (event: string, cb: Function) => void
    emit: (event: string, data: any) => void
    dispose: () => void
    onboard: (registrations: Partial<Z>[]) => Z[]
    size: number
  }
  
  interface RegistryOptions {
    events?: boolean
  }

• Details

  • collection: A JavaScript Map↗ that holds registered items, indexed by their unique IDs.
  • clear(): Clears the entire registry, removing all registered items.
  • has(id: ID): Checks if an item with the given ID exists in the registry.
  • keys(): Returns an array of all registered IDs.
  • browse(value: unknown): Searches for an ID by its value. Returns a single ID if found, or an array of IDs if multiple items match.
  • lookup(index: number): Looks up an ID by its index number.
  • get(id: ID): Retrieves a ticket by its ID, returning undefined if not found.
  • upsert(id: ID, patch?: Partial<Z>): Creates or updates a ticket by its ID. If the ID does not exist, it creates a new ticket; if it does exist, it updates the existing ticket with the provided patch.
  • values(): Returns an array of all registered tickets.
  • entries(): Returns an array of entries, each being a tuple of [ID, ticket].
  • register(item?: Partial<Z>): Registers a new item, returning the created ticket. If item is provided, it will be merged with the default ticket structure.
  • unregister(id: ID): Unregisters an item by its ID, removing it from the registry.
  • reindex(): Rebuilds the index of registered items, useful if the order of items has changed.
  • seek(direction?, from?, predicate?): Searches for a ticket based on direction (‘first’ or ‘last’), optional starting index, and optional predicate function.
  • on(event: string, cb: Function): Registers an event listener for a specific event.
  • off(event: string, cb: Function): Unregisters an event listener for a specific event.
  • emit(event: string, data: any): Emits an event with the provided data, triggering all registered listeners for that event.
  • dispose(): Resets the collection and clears all listeners. Useful to call during onScopeDispose to clean up resources.
  • onboard(registrations: Partial<Z>[]): Registers multiple items in a single call, returning an array of tickets.
  • size: Returns the number of registered items in the registry.

• Options

  • events: If true, enables event emission for registry operations like register and unregister. Defaults to false.

register

• Type

  function register (item?: Partial<Z>): Z

• Details Registers a new item. Behavior rules:

  • If value is omitted, the ticket’s value is set to its (possibly provided) index and valueIsIndex is true.
  • If value is provided (even null), valueIsIndex is false.
  • The index assigned at registration is immutable via upsert (only reindex() can change ordering indices globally). Returns the created ticket.

• Example

  const registry = useRegistry()
  
  const ticket = registry.register({ id: 'foo', value: 'bar' })
  
  console.log(ticket) // { id: 'foo', index: 0, value: 'bar', valueIsIndex: false }

get

• Type

  function get (id: ID): Z | undefined

• Details Retrieves a registered item by its ID. Returns undefined if the item does not exist

• Example

  const registry = useRegistry()
  
  registry.register({ id: 'foo' })
  
  const found = registry.get('foo')
  const notfound = registry.get('bar')

upsert

• Type

  function upsert (id: ID, patch?: Partial<Z>): Z

• Details Creates a ticket when the id does not exist (following the same rules as register), otherwise updates the existing ticket. Special handling only applies to value:

  • Supplying a new value sets valueIsIndex to false.
  • Supplying value: undefined resets value to the ticket’s immutable index and sets valueIsIndex to true.
  • Omitting value leaves both value and valueIsIndex unchanged.
  • The index of an existing ticket is never changed by upsert.

• Example

  const registry = useRegistry()
  
  registry.register({ id: 1 })
  registry.upsert(1, { value: 'custom' })
  registry.upsert(1, { value: undefined })
  
  console.log(registry.get(1)) // { id: 1, index: 0, value: 0, valueIsIndex: true }
  
  registry.upsert(2, { value: 'new' }) // creates new ticket

clear

• Type

  function clear(): void

• Details Removes all registered items from the registry, resetting it to an empty state.

• Example

  const registry = useRegistry()
  
  registry.register({ id: 'a', value: 'Apple' })
  registry.register({ id: 'b', value: 'Banana' })
  
  console.log(registry.size) // 2
  
  registry.clear()
  
  console.log(registry.size) // 0
  console.log(registry.get('a')) // undefined

has

• Type

  function has(id: ID): boolean

• Details Checks whether the registry contains an item with the given ID.

• Example

  const registry = useRegistry()
  registry.register({ id: 'x', value: 'Xylophone' })
  
  console.log(registry.has('x')) // true
  console.log(registry.has('y')) // false

keys

• Type

  function keys(): ID[]

• Details Returns an array of all registered IDs in the order they were indexed. Performance Note: The result is cached for efficiency, meaning repeated calls to keys() reuse a stored array instead of reconstructing it every time. If the registry changes (items are registered or unregistered), the cache is refreshed automatically.

• Example

  const registry = useRegistry()
  registry.register({ id: 'cat', value: 'Cat' })
  registry.register({ id: 'dog', value: 'Dog' })
  
  console.log(registry.keys())
  // ['cat', 'dog']

browse

• Type

  function browse(value: unknown): ID | ID[] | undefined

• Details Searches the registry for item(s) whose value matches the provided value argument.

  If exactly one item matches, browse returns that item’s ID directly. If multiple items have the same value, browse returns an array of matching IDs, preserving their registration order. If no match is found, it returns undefined.

  This allows both quick single lookups and detection of duplicates. For consistency, if you expect possible duplicates, always handle both single-ID and array return types in your code.

• Example

  const registry = useRegistry()
  registry.register({ id: '1', value: 'Red' })
  registry.register({ id: '2', value: 'Blue' })
  registry.register({ id: '3', value: 'Red' }) // Duplicate value
  
  console.log(registry.browse('Red'))
  // ['1', '3']  <-- Multiple matches return array
  
  console.log(registry.browse('Blue'))
  // '2'  <-- Single match returns ID
  
  console.log(registry.browse('Green'))
  // undefined  <-- No matches

lookup

• Type

  function lookup(index: number): ID | undefined

• Details Finds the ID of the item at a given index position in the registry.

• Example

  const registry = useRegistry()
  registry.register({ id: 'apple', value: 'Apple' })
  registry.register({ id: 'banana', value: 'Banana' })
  
  console.log(registry.lookup(0)) // 'apple'
  console.log(registry.lookup(1)) // 'banana'
  console.log(registry.lookup(5)) // undefined

values

• Type

  function values(): Z[]

• Details Returns an array of all registered items. Performance Note: The result is cached internally to avoid reconstructing the list on every call. The cache is automatically invalidated and rebuilt whenever the registry changes, so you always get the latest data without unnecessary overhead.

• Example

  const registry = useRegistry()
  registry.register({ id: 'x', value: 'X' })
  registry.register({ id: 'y', value: 'Y' })
  
  console.log(registry.values())
  // [ { id: 'x', value: 'X' }, { id: 'y', value: 'Y' } ]

entries

• Type

  function entries(): [ID, Z][]

• Details Returns all registry entries as [id, item] pairs. Performance Note: Like keys() and values(), the results of entries() are cached for performance. The cache is refreshed whenever the registry is modified, so calls remain fast and up-to-date.

• Example

  const registry = useRegistry()
  registry.register({ id: 'car', value: 'Car' })
  registry.register({ id: 'bus', value: 'Bus' })
  
  for (const [id, item] of registry.entries()) {
    console.log(id, item.value)
  }
  // car Car
  // bus Bus

unregister

• Type

  function unregister(id: ID): void

• Details Removes an item from the registry by its ID.

• Example

  const registry = useRegistry()
  registry.register({ id: 'x', value: 'Xylophone' })
  
  registry.unregister('x')
  
  console.log(registry.has('x')) // false

onboard

• Type

  function onboard(registrations: Partial<Z>[]): Z[]

• Details Registers multiple items in a single call. onboard simply calls register for each object in the input array, in order, and returns an array of the resulting tickets. It preserves registration order and will apply the same rules as register for id generation, index assignment, value defaults, caching and event emission (if events is enabled).

• Example

  const registry = useRegistry()
  
  const tickets = registry.onboard([
    { id: 'a', value: 'Apple' },
    { value: 'Banana' }, // id generated automatically
    { id: 'a', value: 'Duplicate' } // duplicate id -> returns existing ticket
  ])
  
  console.log(tickets.length) // 3
  console.log(registry.size) // 2 (third reused existing)

reindex

• Type

  function reindex(): void

• Details Recalculates the index numbers for all registered items, useful after order changes.

• Example

  const registry = useRegistry()
  registry.register({ id: 'first', value: 'First' })
  registry.register({ id: 'second', value: 'Second' })
  
  // Simulate moving items
  registry.unregister('first')
  registry.register({ id: 'first', value: 'First' })
  
  registry.reindex()
  console.log(registry.lookup(0)) // 'second'
  console.log(registry.lookup(1)) // 'first'

seek

• Type

  function seek(
    direction?: 'first' | 'last',
    from?: number,
    predicate?: (ticket: Z) => boolean
  ): Z | undefined

• Details Searches for a ticket based on direction and an optional predicate function.

  • direction: The direction to seek - 'first' (default) searches from start to end, 'last' searches from end to start
  • from: Optional starting index position. Defaults to beginning/end based on direction
  • predicate: Optional filter function. Returns the first ticket that satisfies the predicate

  Returns undefined if no matching ticket is found.

• Example

  const registry = useRegistry()
  
  registry.register({ id: 'ticket-1', value: 'apple' })
  registry.register({ id: 'ticket-2', value: 'banana' })
  registry.register({ id: 'ticket-3', value: 'cherry' })
  
  // Get first ticket
  const first = registry.seek('first')
  console.log(first?.value) // 'apple'
  
  // Get last ticket
  const last = registry.seek('last')
  console.log(last?.value) // 'cherry'
  
  // Find first ticket with value 'banana'
  const banana = registry.seek('first', undefined, ticket => ticket.value === 'banana')
  console.log(banana?.id) // 'ticket-2'
  
  // Seek from index 1 to find the next ticket with value starting with 'c'
  const cherry = registry.seek('first', 1, ticket =>
    (ticket.value as string).startsWith('c')
  )
  console.log(cherry?.value) // 'cherry'

on

• Type

  function on(event: string, cb: Function): void

• Details Attaches a listener for a specific event (only if events are enabled).

• Example

  const registry = useRegistry()
  
  registry.on('register', item => {
    console.log('Registered:', item)
  })
  
  registry.register({ id: '1', value: 'New Item' })
  // Output: Registered: { id: '1', value: 'New Item' }

off

• Type

  function off(event: string, cb: Function): void

• Details Removes a previously attached event listener.

• Example

  const registry = useRegistry()
  
  function logItem(item) {
    console.log('Registered:', item)
  }
  
  registry.on('register', logItem)
  registry.off('register', logItem)

emit

• Type

  function emit(event: string, data: any): void

• Details Manually triggers an event, passing optional data to listeners.

• Example

  const registry = useRegistry()
  
  registry.on('custom', payload => {
    console.log('Custom event data:', payload)
  })
  
  registry.emit('custom', { foo: 'bar' })
  // Output: Custom event data: { foo: 'bar' }

dispose

• Type

  function dispose(): void

• Details Resets the registry and clears all event listeners. This is useful for cleaning up resources when the registry is no longer needed, such as when a component is destroyed or a scope ends.

• Example

  import { onScopeDispose } from 'vue'
  
  const registry = useRegistry()
  
  onScopeDispose(() => {
    registry.dispose()
  })

size

• Type

  number

• Details The total count of registered items in the registry.

• Example

  const registry = useRegistry()
  registry.register({ id: 'a', value: 'Apple' })
  registry.register({ id: 'b', value: 'Banana' })
  
  console.log(registry.size) // 2