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QueryList
Class
stable
An unmodifiable list of items that Angular keeps up to date when the state of the application changes.
API
class QueryList<T> implements Iterable<T> { constructor(_emitDistinctChangesOnly?: boolean): QueryList<T>; readonly dirty: true; readonly length: number; readonly first: T; readonly last: T; readonly changes: Observable<any>; get(index: number): T | undefined; map<U>(fn: (item: T, index: number, array: T[]) => U): U[]; filter<S extends T>(predicate: (value: T, index: number, array: readonly T[]) => value is S): S[]; filter(predicate: (value: T, index: number, array: readonly T[]) => unknown): 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) | undefined): void; notifyOnChanges(): void; setDirty(): void; destroy(): void; [Symbol.iterator]: () => Iterator<T, any, any>;}
constructor
QueryList<T>@param_emitDistinctChangesOnly
boolean@returns
QueryList<T>dirty
truelength
numberlast
Tget
T | undefinedReturns the QueryList entry at index.
@paramindex
number@returns
T | undefinedfilter
2 overloadsSee Array.filter
@parampredicate
(value: T, index: number, array: readonly T[]) => value is S@returns
S[]@parampredicate
(value: T, index: number, array: readonly T[]) => unknown@returns
T[]find
T | undefinedreduce
USee Array.reduce
@paramfn
(prevValue: U, curValue: T, curIndex: number, array: T[]) => U@paraminit
U@returns
UforEach
voidsome
booleantoArray
T[]Returns a copy of the internal results list as an Array.
@returns
T[]toString
string@returns
stringreset
voidUpdates 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.
@paramresultsTree
(any[] | T)[]The query results to store
@paramidentityAccessor
((value: T) => unknown) | undefinedOptional 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).
@returns
voidnotifyOnChanges
voidTriggers a change event by emitting on the changes EventEmitter.
@returns
voidsetDirty
voidinternal
@returns
voiddestroy
voidinternal
@returns
void[Symbol.iterator]
() => Iterator<T, any, any>Description
An unmodifiable list of items that Angular keeps up to date when the state of the application changes.
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
@for(i of myList; track $index).
Changes can be observed by subscribing to the changes Observable.
*
Usage Notes
Example
@Component({...})
class Container {
@ViewChildren(Item) items:QueryList<Item>;
}Jump to details