QueryList

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

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class QueryList<T> {
  dirty: true
  changes: Observable<any>
  length: number
  first: T
  last: T
  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(res: (any[] | T)[]): 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.

Properties

Property	Description
dirty: true	Read-only.
changes: Observable<any>	Read-only.
length: number	Read-only.
first: T	Read-only.
last: T	Read-only.

Methods

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()
toArray(): T[] Parameters There are no parameters. Returns T[]

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

reset()
reset(res: (any[] | T)[]): void Parameters res (any[] | T)[] Returns void

notifyOnChanges()
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>;
}