An unmodifiable list of items that Angular keeps up to date when the state of the application changes.

See more...

class QueryList<T> implements Iterable<T> {
  constructor(_emitDistinctChangesOnly: boolean = false)
  dirty: true
  length: number
  first: T
  last: T
  changes: Observable<any>
  __@iterator: () => Iterator<T>
  get(index: number): T | undefined
  map<U>(fn: (item: T, index: number, array: T[]) => U): U[]
  filter(fn: (item: T, index: number, array: T[]) => boolean): T[]
  find(fn: (item: T, index: number, array: T[]) => boolean): T | undefined
  reduce<U>(fn: (prevValue: U, curValue: T, curIndex: number, array: T[]) => U, init: U): U
  forEach(fn: (item: T, index: number, array: T[]) => void): void
  some(fn: (value: T, index: number, array: T[]) => boolean): boolean
  toArray(): T[]
  toString(): string
  reset(resultsTree: (any[] | T)[], identityAccessor?: (value: T) => unknown): void
  notifyOnChanges(): void
  setDirty()
  destroy(): void
}

Description

The type of object that ViewChildren, ContentChildren, and QueryList provide.

Implements an iterable interface, therefore it can be used in both ES6 javascript for (var i of items) loops as well as in Angular templates with *ngFor="let i of myList".

Changes can be observed by subscribing to the changes Observable.

NOTE: In the future this class will implement an Observable interface.

Further information is available in the Usage Notes...

Constructor

constructor(_emitDistinctChangesOnly: boolean = false) Parameters _emitDistinctChangesOnly boolean Optional. Default is false.

Properties

Property	Description
dirty: true	Read-Only
length: number	Read-Only
first: T	Read-Only
last: T	Read-Only
changes: Observable<any>	Read-Only Returns Observable of QueryList notifying the subscriber of changes.
__@iterator: () => Iterator<T>

Methods

get()
Returns the QueryList entry at index.
get(index: number): T | undefined Parameters index number Returns T | undefined

map()
See Array.map
map<U>(fn: (item: T, index: number, array: T[]) => U): U[] Parameters fn (item: T, index: number, array: T[]) => U Returns U[]

filter()
See Array.filter
filter(fn: (item: T, index: number, array: T[]) => boolean): T[] Parameters fn (item: T, index: number, array: T[]) => boolean Returns T[]

find()
See Array.find
find(fn: (item: T, index: number, array: T[]) => boolean): T | undefined Parameters fn (item: T, index: number, array: T[]) => boolean Returns T | undefined

reduce()
See Array.reduce
reduce<U>(fn: (prevValue: U, curValue: T, curIndex: number, array: T[]) => U, init: U): U Parameters fn (prevValue: U, curValue: T, curIndex: number, array: T[]) => U init U Returns U

forEach()
See Array.forEach
forEach(fn: (item: T, index: number, array: T[]) => void): void Parameters fn (item: T, index: number, array: T[]) => void Returns void

some()
See Array.some
some(fn: (value: T, index: number, array: T[]) => boolean): boolean Parameters fn (value: T, index: number, array: T[]) => boolean Returns boolean

toArray()
Returns a copy of the internal results list as an Array.
toArray(): T[] Parameters There are no parameters. Returns T[]

toString()
toString(): string Parameters There are no parameters. Returns string

reset()
Updates the stored data of the query list, and resets the dirty flag to false, so that on change detection, it will not notify of changes to the queries, unless a new change occurs.
reset(resultsTree: (any[] | T)[], identityAccessor?: (value: T) => unknown): void Parameters resultsTree (any[] | T)[] The query results to store identityAccessor (value: T) => unknown Optional function for extracting stable object identity from a value in the array. This function is executed for each element of the query result list while comparing current query list with the new one (provided as a first argument of the reset function) to detect if the lists are different. If the function is not provided, elements are compared as is (without any pre-processing). Optional. Default is undefined. Returns void

notifyOnChanges()
Triggers a change event by emitting on the changes EventEmitter.
notifyOnChanges(): void Parameters There are no parameters. Returns void

setDirty()
internal
setDirty() Parameters There are no parameters.

destroy()
internal
destroy(): void Parameters There are no parameters. Returns void

Usage notes

Example

@Component({...})
class Container {
  @ViewChildren(Item) items:QueryList<Item>;
}