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docs: add doc to focusBoundControl feature #67667
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| Original file line number | Diff line number | Diff line change | ||
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@@ -721,6 +721,85 @@ export class StyleExample { | |||
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| Checking both `touched()` and validation state ensures styles only appear after the user has interacted with the field. | ||||
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| ## Focus a form control bound to a form field | ||||
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| Angular Signal Forms provide a `focusBoundControl()` method on field state that lets you programmatically move [focus](https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/focus) to the form control associated with a given form field. | ||||
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| A common use case is improving accessibility on form submission: when a form is invalid, display error messages and automatically move focus to the first invalid field, guiding the user to correct it. | ||||
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| ### Basic usage | ||||
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| Given a registration form: | ||||
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| ```ts | ||||
| @Component({/* ... */}) | ||||
| export class Registration { | ||||
| registrationModel = signal({ username: '', email: '', password: '' }); | ||||
| registrationForm = form(this.registrationModel, (schemaPath) => { | ||||
| required(schemaPath.username); | ||||
| email(schemaPath.email); | ||||
| required(schemaPath.password); | ||||
| }); | ||||
| } | ||||
| ``` | ||||
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| To move focus to the control bound to the `email` field: | ||||
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| ```ts | ||||
| registrationForm.email().focusBoundControl(); | ||||
| ``` | ||||
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| ### Preventing scroll | ||||
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| If the target control is outside the viewport and you want to focus it without triggering a scroll, you can set the [preventScroll](https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/focus#preventscroll) option to `true` when calling the `focusBoundControl()` method. | ||||
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| ```ts | ||||
| registrationForm.email().focusBoundControl({ preventScroll: true }); | ||||
| ``` | ||||
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Contributor
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Suggested change
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| ### Focusing the first invalid field on submission | ||||
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| Use `errorSummary()` to locate the first invalid field and focus it when the user submits the form with errors: | ||||
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| ```ts | ||||
| onSubmit() { | ||||
| const firstError = this.registrationForm().errorSummary()[0]; | ||||
| if (firstError?.fieldTree) { | ||||
| firstError.fieldTree().focusBoundControl(); | ||||
| } else { | ||||
| // proceed with submission | ||||
| } | ||||
| } | ||||
| ``` | ||||
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| ### Custom controls | ||||
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| By default, calling `focusBoundControl()` on a custom control has no effect because a custom control can contain multiple native inputs. For example, a date picker can contain separate day, month, and year fields. As a result, Angular cannot determine which element should receive focus or what action to perform. | ||||
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| To support programmatic focus in a custom control, implement a `focus()` method. When `focusBoundControl()` is called on the field state associated with a custom control, Angular calls the control's `focus()` method if one is present. | ||||
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| Consider a custom password input: | ||||
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| ```html | ||||
| <div class="password-block"> | ||||
| <input type="password" #passwordCtrl [value]="value()" (input)="value.set($event.target.value)" /> | ||||
| </div> | ||||
| ``` | ||||
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| ```ts | ||||
| @Component({/* ... */}) | ||||
| export class PasswordInput implements FormValueControl<string> { | ||||
| readonly value = model<string>(''); | ||||
| readonly passwordCtrl = viewChild.required<ElementRef<HTMLInputElement>>('passwordCtrl'); | ||||
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| // Called automatically when focusBoundControl() is invoked | ||||
| // on the field state associated with this custom control | ||||
| focus(): void { | ||||
| this.passwordCtrl().nativeElement.focus(); | ||||
| } | ||||
| } | ||||
| ``` | ||||
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Contributor
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Suggested change
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| ## Next steps | ||||
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| This guide covered validation and availability status handling, interaction tracking and field state propagation. Related guides explore other aspects of Signal Forms: | ||||
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