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FormArray

class

Tracks the value and validity state of an array of FormControl, FormGroup or FormArray instances.

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class FormArray extends AbstractControl {
  constructor(controls: AbstractControl[], validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[])
  controls: AbstractControl[]
  length: number
  at(index: number): AbstractControl
  push(control: AbstractControl): void
  insert(index: number, control: AbstractControl): void
  removeAt(index: number): void
  setControl(index: number, control: AbstractControl): void
  setValue(value: any[], options: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  patchValue(value: any[], options: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  reset(value: any = [], options: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  getRawValue(): any[]
  clear(): void

  // inherited from forms/AbstractControl
  constructor(validator: ValidatorFn, asyncValidator: AsyncValidatorFn)
  value: any
  validator: ValidatorFn | null
  asyncValidator: AsyncValidatorFn | null
  parent: FormGroup | FormArray
  status: string
  valid: boolean
  invalid: boolean
  pending: boolean
  disabled: boolean
  enabled: boolean
  errors: ValidationErrors | null
  pristine: boolean
  dirty: boolean
  touched: boolean
  untouched: boolean
  valueChanges: Observable<any>
  statusChanges: Observable<any>
  updateOn: FormHooks
  root: AbstractControl
  setValidators(newValidator: ValidatorFn | ValidatorFn[]): void
  setAsyncValidators(newValidator: AsyncValidatorFn | AsyncValidatorFn[]): void
  clearValidators(): void
  clearAsyncValidators(): void
  markAsTouched(opts: { onlySelf?: boolean; } = {}): void
  markAllAsTouched(): void
  markAsUntouched(opts: { onlySelf?: boolean; } = {}): void
  markAsDirty(opts: { onlySelf?: boolean; } = {}): void
  markAsPristine(opts: { onlySelf?: boolean; } = {}): void
  markAsPending(opts: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  disable(opts: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  enable(opts: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  setParent(parent: FormGroup | FormArray): void
  abstract setValue(value: any, options?: Object): void
  abstract patchValue(value: any, options?: Object): void
  abstract reset(value?: any, options?: Object): void
  updateValueAndValidity(opts: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void
  setErrors(errors: ValidationErrors, opts: { emitEvent?: boolean; } = {}): void
  get(path: string | (string | number)[]): AbstractControl | null
  getError(errorCode: string, path?: string | (string | number)[]): any
  hasError(errorCode: string, path?: string | (string | number)[]): boolean
}

Description

A FormArray aggregates the values of each child FormControl into an array. It calculates its status by reducing the status values of its children. For example, if one of the controls in a FormArray is invalid, the entire array becomes invalid.

FormArray is one of the three fundamental building blocks used to define forms in Angular, along with FormControl and FormGroup.

Constructor

Creates a new FormArray instance.

constructor(controls: AbstractControl[], validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[])

Parameters
controls AbstractControl[]

An array of child controls. Each child control is given an index where it is registered.

validatorOrOpts ValidatorFn | AbstractControlOptions | ValidatorFn[]

A synchronous validator function, or an array of such functions, or an AbstractControlOptions object that contains validation functions and a validation trigger.

Optional. Default is undefined.

asyncValidator AsyncValidatorFn | AsyncValidatorFn[]

A single async validator or array of async validator functions

Optional. Default is undefined.

Properties

Property Description
controls: AbstractControl[] Declared in Constructor

An array of child controls. Each child control is given an index where it is registered.

length: number Read-Only

Length of the control array.

Methods

Get the AbstractControl at the given index in the array.

at(index: number): AbstractControl

Parameters
index number

Index in the array to retrieve the control

Returns

AbstractControl

Insert a new AbstractControl at the end of the array.

push(control: AbstractControl): void

Parameters
control AbstractControl

Form control to be inserted

Returns

void

Insert a new AbstractControl at the given index in the array.

insert(index: number, control: AbstractControl): void

Parameters
index number

Index in the array to insert the control

control AbstractControl

Form control to be inserted

Returns

void

Remove the control at the given index in the array.

removeAt(index: number): void

Parameters
index number

Index in the array to remove the control

Returns

void

Replace an existing control.

setControl(index: number, control: AbstractControl): void

Parameters
index number

Index in the array to replace the control

control AbstractControl

The AbstractControl control to replace the existing control

Returns

void

Sets the value of the FormArray. It accepts an array that matches the structure of the control.

setValue(value: any[], options: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void

Parameters
value any[]

Array of values for the controls

options object

Configure options that determine how the control propagates changes and emits events after the value changes

  • onlySelf: When true, each change only affects this control, and not its parent. Default is false.
  • emitEvent: When true or not supplied (the default), both the statusChanges and valueChanges observables emit events with the latest status and value when the control value is updated. When false, no events are emitted. The configuration options are passed to the updateValueAndValidity method.

Optional. Default is {}.

Returns

void

This method performs strict checks, and throws an error if you try to set the value of a control that doesn't exist or if you exclude the value of a control.

Usage Notes

Set the values for the controls in the form array
const arr = new FormArray([
  new FormControl(),
  new FormControl()
]);
console.log(arr.value);   // [null, null]

arr.setValue(['Nancy', 'Drew']);
console.log(arr.value);   // ['Nancy', 'Drew']

Patches the value of the FormArray. It accepts an array that matches the structure of the control, and does its best to match the values to the correct controls in the group.

patchValue(value: any[], options: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void

Parameters
value any[]

Array of latest values for the controls

options object

Configure options that determine how the control propagates changes and emits events after the value changes

  • onlySelf: When true, each change only affects this control, and not its parent. Default is false.
  • emitEvent: When true or not supplied (the default), both the statusChanges and valueChanges observables emit events with the latest status and value when the control value is updated. When false, no events are emitted. The configuration options are passed to the updateValueAndValidity method.

Optional. Default is {}.

Returns

void

It accepts both super-sets and sub-sets of the array without throwing an error.

Usage Notes

Patch the values for controls in a form array
const arr = new FormArray([
   new FormControl(),
   new FormControl()
]);
console.log(arr.value);   // [null, null]

arr.patchValue(['Nancy']);
console.log(arr.value);   // ['Nancy', null]

Resets the FormArray and all descendants are marked pristine and untouched, and the value of all descendants to null or null maps.

reset(value: any = [], options: { onlySelf?: boolean; emitEvent?: boolean; } = {}): void

Parameters
value any

Array of values for the controls

Optional. Default is [].

options object

Configure options that determine how the control propagates changes and emits events after the value changes

  • onlySelf: When true, each change only affects this control, and not its parent. Default is false.
  • emitEvent: When true or not supplied (the default), both the statusChanges and valueChanges observables emit events with the latest status and value when the control is reset. When false, no events are emitted. The configuration options are passed to the updateValueAndValidity method.

Optional. Default is {}.

Returns

void

You reset to a specific form state by passing in an array of states that matches the structure of the control. The state is a standalone value or a form state object with both a value and a disabled status.

Usage Notes

Reset the values in a form array
const arr = new FormArray([
   new FormControl(),
   new FormControl()
]);
arr.reset(['name', 'last name']);

console.log(this.arr.value);  // ['name', 'last name']
Reset the values in a form array and the disabled status for the first control
this.arr.reset([
  {value: 'name', disabled: true},
  'last'
]);

console.log(this.arr.value);  // ['name', 'last name']
console.log(this.arr.get(0).status);  // 'DISABLED'

The aggregate value of the array, including any disabled controls.

getRawValue(): any[]

Parameters

There are no parameters.

Returns

any[]

Reports all values regardless of disabled status. For enabled controls only, the value property is the best way to get the value of the array.

Remove all controls in the FormArray.

clear(): void

Parameters

There are no parameters.

Returns

void

Usage Notes

Remove all elements from a FormArray
const arr = new FormArray([
   new FormControl(),
   new FormControl()
]);
console.log(arr.length);  // 2

arr.clear();
console.log(arr.length);  // 0

It's a simpler and more efficient alternative to removing all elements one by one:

const arr = new FormArray([
   new FormControl(),
   new FormControl()
]);

while (arr.length) {
   arr.removeAt(0);
}

Usage notes

Create an array of form controls

const arr = new FormArray([
  new FormControl('Nancy', Validators.minLength(2)),
  new FormControl('Drew'),
]);

console.log(arr.value);   // ['Nancy', 'Drew']
console.log(arr.status);  // 'VALID'

Create a form array with array-level validators

You include array-level validators and async validators. These come in handy when you want to perform validation that considers the value of more than one child control.

The two types of validators are passed in separately as the second and third arg respectively, or together as part of an options object.

const arr = new FormArray([
  new FormControl('Nancy'),
  new FormControl('Drew')
], {validators: myValidator, asyncValidators: myAsyncValidator});

Set the updateOn property for all controls in a form array

The options object is used to set a default value for each child control's updateOn property. If you set updateOn to 'blur' at the array level, all child controls default to 'blur', unless the child has explicitly specified a different updateOn value.

const arr = new FormArray([
   new FormControl()
], {updateOn: 'blur'});

Adding or removing controls from a form array

To change the controls in the array, use the push, insert, removeAt or clear methods in FormArray itself. These methods ensure the controls are properly tracked in the form's hierarchy. Do not modify the array of AbstractControls used to instantiate the FormArray directly, as that result in strange and unexpected behavior such as broken change detection.

© 2010–2019 Google, Inc.
Licensed under the Creative Commons Attribution License 4.0.
https://angular.io/api/forms/FormArray