/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { InjectionToken } from '@angular/core';
/**
 * @description
 * Defines an interface that acts as a bridge between the Angular forms API and a
 * native element in the DOM.
 *
 * Implement this interface to create a custom form control directive
 * that integrates with Angular forms.
 *
 * @see DefaultValueAccessor
 *
 * @publicApi
 */
export interface ControlValueAccessor {
    /**
     * @description
     * Writes a new value to the element.
     *
     * This method is called by the forms API to write to the view when programmatic
     * changes from model to view are requested.
     *
     * @usageNotes
     * ### Write a value to the element
     *
     * The following example writes a value to the native DOM element.
     *
     * ```ts
     * writeValue(value: any): void {
     *   this._renderer.setProperty(this._elementRef.nativeElement, 'value', value);
     * }
     * ```
     *
     * @param obj The new value for the element
     */
    writeValue(obj: any): void;
    /**
     * @description
     * Registers a callback function that is called when the control's value
     * changes in the UI.
     *
     * This method is called by the forms API on initialization to update the form
     * model when values propagate from the view to the model.
     *
     * When implementing the `registerOnChange` method in your own value accessor,
     * save the given function so your class calls it at the appropriate time.
     *
     * @usageNotes
     * ### Store the change function
     *
     * The following example stores the provided function as an internal method.
     *
     * ```ts
     * registerOnChange(fn: (_: any) => void): void {
     *   this._onChange = fn;
     * }
     * ```
     *
     * When the value changes in the UI, call the registered
     * function to allow the forms API to update itself:
     *
     * ```ts
     * host: {
     *    (change): '_onChange($event.target.value)'
     * }
     * ```
     *
     * @param fn The callback function to register
     */
    registerOnChange(fn: any): void;
    /**
     * @description
     * Registers a callback function is called by the forms API on initialization
     * to update the form model on blur.
     *
     * When implementing `registerOnTouched` in your own value accessor, save the given
     * function so your class calls it when the control should be considered
     * blurred or "touched".
     *
     * @usageNotes
     * ### Store the callback function
     *
     * The following example stores the provided function as an internal method.
     *
     * ```ts
     * registerOnTouched(fn: any): void {
     *   this._onTouched = fn;
     * }
     * ```
     *
     * On blur (or equivalent), your class should call the registered function to allow
     * the forms API to update itself:
     *
     * ```ts
     * host: {
     *    '(blur)': '_onTouched()'
     * }
     * ```
     *
     * @param fn The callback function to register
     */
    registerOnTouched(fn: any): void;
    /**
     * @description
     * Function that is called by the forms API when the control status changes to
     * or from 'DISABLED'. Depending on the status, it enables or disables the
     * appropriate DOM element.
     *
     * @usageNotes
     * The following is an example of writing the disabled property to a native DOM element:
     *
     * ```ts
     * setDisabledState(isDisabled: boolean): void {
     *   this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
     * }
     * ```
     *
     * @param isDisabled The disabled status to set on the element
     */
    setDisabledState?(isDisabled: boolean): void;
}
/**
 * Used to provide a `ControlValueAccessor` for form controls.
 *
 * See `DefaultValueAccessor` for how to implement one.
 *
 * @publicApi
 */
export declare const NG_VALUE_ACCESSOR: InjectionToken<ControlValueAccessor>;
