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FormBuilder

class final

Creates an AbstractControl from a user-specified configuration.

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class FormBuilder {
  nonNullable: NonNullableFormBuilder
  group(controls: { [key: string]: any; }, options: AbstractControlOptions | { [key: string]: any; } = null): FormGroup
  record<T>(controls: { [key: string]: T; }, options: AbstractControlOptions = null): FormRecord<ɵElement<T, null>>
  control<T>(formState: T | FormControlState<T>, validatorOrOpts?: ValidatorFn | FormControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormControl
  array<T>(controls: T[], validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormArray<ɵElement<T, null>>
}

Subclasses

See also

Provided in

  • 'root'

Description

The FormBuilder provides syntactic sugar that shortens creating instances of a FormControl, FormGroup, or FormArray. It reduces the amount of boilerplate needed to build complex forms.

Properties

Property Description
nonNullable: NonNullableFormBuilder Read-Only

Returns a FormBuilder in which automatically constructed FormControl elements have {nonNullable: true} and are non-nullable.

Constructing non-nullable controls

When constructing a control, it will be non-nullable, and will reset to its initial value.

let nnfb = new FormBuilder().nonNullable;
let name = nnfb.control('Alex'); // FormControl<string>
name.reset();
console.log(name); // 'Alex'

Constructing non-nullable groups or arrays

When constructing a group or array, all automatically created inner controls will be non-nullable, and will reset to their initial values.

let nnfb = new FormBuilder().nonNullable;
let name = nnfb.group({who: 'Alex'}); // FormGroup<{who: FormControl<string>}>
name.reset();
console.log(name); // {who: 'Alex'}

Constructing nullable fields on groups or arrays

It is still possible to have a nullable field. In particular, any FormControl which is already constructed will not be altered. For example:

let nnfb = new FormBuilder().nonNullable;
// FormGroup<{who: FormControl<string|null>}>
let name = nnfb.group({who: new FormControl('Alex')});
name.reset(); console.log(name); // {who: null}

Because the inner control is constructed explicitly by the caller, the builder has no control over how it is created, and cannot exclude the null.

Methods

group()

Constructs a new FormGroup instance. Accepts a single generic argument, which is an object containing all the keys and corresponding inner control types.

group<T extends {}>(controls: T, options?: AbstractControlOptions): FormGroup<{ [K in keyof T]: ɵElement<T[K], null>; }>

Parameters
controls T

A collection of child controls. The key for each child is the name under which it is registered.
options AbstractControlOptions

Configuration options object for the FormGroup. The object should have the AbstractControlOptions type and might contain the following fields:

  • validators: A synchronous validator function, or an array of validator functions.
  • asyncValidators: A single async validator or array of async validator functions.
  • updateOn: The event upon which the control should be updated (options: 'change' | 'blur' | submit').

Optional. Default is undefined.
Returns

FormGroup<{ [K in keyof T]: ɵElement<T[K], null>; }>

Constructs a new FormGroup instance.

group(controls: { [key: string]: any; }, options: { [key: string]: any; }): FormGroup

Deprecated This API is not typesafe and can result in issues with Closure Compiler renaming. Use the FormBuilder#group overload with AbstractControlOptions instead. Note that AbstractControlOptions expects validators and asyncValidators to be valid validators. If you have custom validators, make sure their validation function parameter is AbstractControl and not a sub-class, such as FormGroup. These functions will be called with an object of type AbstractControl and that cannot be automatically downcast to a subclass, so TypeScript sees this as an error. For example, change the (group: FormGroup) => ValidationErrors|null signature to be (group: AbstractControl) => ValidationErrors|null.

Parameters
controls object

A record of child controls. The key for each child is the name under which the control is registered.
options object

Configuration options object for the FormGroup. The legacy configuration object consists of:

  • validator: A synchronous validator function, or an array of validator functions.
  • asyncValidator: A single async validator or array of async validator functions Note: the legacy format is deprecated and might be removed in one of the next major versions of Angular.
Returns

FormGroup
record()

Constructs a new FormRecord instance. Accepts a single generic argument, which is an object containing all the keys and corresponding inner control types.

record<T>(controls: { [key: string]: T; }, options: AbstractControlOptions = null): FormRecord<ɵElement<T, null>>

Parameters
controls object

A collection of child controls. The key for each child is the name under which it is registered.
options AbstractControlOptions

Configuration options object for the FormRecord. The object should have the AbstractControlOptions type and might contain the following fields:

  • validators: A synchronous validator function, or an array of validator functions.
  • asyncValidators: A single async validator or array of async validator functions.
  • updateOn: The event upon which the control should be updated (options: 'change' | 'blur' | submit').

Optional. Default is null.
Returns

FormRecord<ɵElement<T, null>>
control()

Constructs a new FormControl with the given state, validators and options. Sets {nonNullable: true} in the options to get a non-nullable control. Otherwise, the control will be nullable. Accepts a single generic argument, which is the type of the control's value.

4 overloads...

Show All Hide All
Overload #1

control<T>(formState: T | FormControlState<T>, opts: FormControlOptions & { initialValueIsDefault: true; }): FormControl<T>

Deprecated Use nonNullable instead.

Parameters
formState T | FormControlState<T>
opts FormControlOptions & { initialValueIsDefault: true; }
Returns

FormControl<T>

Overload #2

control<T>(formState: T | FormControlState<T>, opts: FormControlOptions & { nonNullable: true; }): FormControl<T>

Parameters
formState T | FormControlState<T>
opts FormControlOptions & { nonNullable: true; }
Returns

FormControl<T>

Overload #3

control<T>(formState: T | FormControlState<T>, opts: FormControlOptions, asyncValidator: AsyncValidatorFn | AsyncValidatorFn[]): FormControl<T | null>

Deprecated When passing an options argument, the asyncValidator argument has no effect.

Parameters
formState T | FormControlState<T>
opts FormControlOptions
asyncValidator AsyncValidatorFn | AsyncValidatorFn[]
Returns

FormControl<T | null>

Overload #4

control<T>(formState: T | FormControlState<T>, validatorOrOpts?: ValidatorFn | FormControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormControl<T | null>

Parameters
formState T | FormControlState<T>
validatorOrOpts ValidatorFn | FormControlOptions | ValidatorFn[]

Optional. Default is undefined.
asyncValidator AsyncValidatorFn | AsyncValidatorFn[]

Optional. Default is undefined.
Returns

FormControl<T | null>

Usage Notes

Initialize a control as disabled

The following example returns a control with an initial value in a disabled state.

import {Component, Inject} from '@angular/core';
import {FormBuilder, FormControl, FormGroup, Validators} from '@angular/forms';
/* . . . */
@Component({
  selector: 'app-disabled-form-control',
  template: `
    <input [formControl]="control" placeholder="First">
  `
})
export class DisabledFormControlComponent {
  control: FormControl;

  constructor(private fb: FormBuilder) {
    this.control = fb.control({value: 'my val', disabled: true});
  }
}
array()

Constructs a new FormArray from the given array of configurations, validators and options. Accepts a single generic argument, which is the type of each control inside the array.

array<T>(controls: T[], validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormArray<ɵElement<T, null>>

Parameters
controls T[]

An array of child controls or control configs. Each child control is given an index when 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.
Returns

FormArray<ɵElement<T, null>>

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Licensed under the Creative Commons Attribution License 4.0.
https://angular.io/api/forms/FormBuilder