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/Angular 7

QueryList

class

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

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[]

See Array.filter

filter(fn: (item: T, index: number, array: T[]) => boolean): T[]

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

T[]

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

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

See Array.forEach

forEach(fn: (item: T, index: number, array: T[]) => void): void

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

void

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(): T[]

Parameters

There are no parameters.

Returns

T[]

toString(): string

Parameters

There are no parameters.

Returns

string

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

Parameters
res (any[] | T)[]
Returns

void

notifyOnChanges(): void

Parameters

There are no parameters.

Returns

void

internal

setDirty()

Parameters

There are no parameters.

internal

destroy(): void

Parameters

There are no parameters.

Returns

void

Usage notes

Example

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

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Licensed under the Creative Commons Attribution License 4.0.
https://v7.angular.io/api/core/QueryList