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FormBuilder

class final

Creates an AbstractControl from a user-specified configuration.

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class FormBuilder {
  group(controlsConfig: { [key: string]: any; }, options: AbstractControlOptions | { [key: string]: any; } = null): FormGroup
  control(formState: any, validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormControl
  array(controlsConfig: any[], validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormArray
}

See also

Provided in

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.

Methods

group()

Construct a new FormGroup instance.

group(controlsConfig: { [key: string]: any; }, options?: AbstractControlOptions): FormGroup

Parameters
controlsConfig 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 FormGroup. The object should have the 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

Construct a new FormGroup instance.

group(controlsConfig: { [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
controlsConfig object

A collection of child controls. The key for each child is the name under which it 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
control()

Construct a new FormControl with the given state, validators and options.

control(formState: any, validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormControl

Parameters
formState any

Initializes the control with an initial state value, or with an object that contains both a value and a disabled status.
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

FormControl

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.

array(controlsConfig: any[], validatorOrOpts?: ValidatorFn | AbstractControlOptions | ValidatorFn[], asyncValidator?: AsyncValidatorFn | AsyncValidatorFn[]): FormArray

Parameters
controlsConfig any[]

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

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Licensed under the Creative Commons Attribution License 4.0.
https://v12.angular.io/api/forms/FormBuilder