/**
 * @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';
/**
 * A `ControlValueAccessor` acts as a bridge between the Angular forms API and a
 * native element in the DOM.
 *
 * Implement this interface if you want to create a custom form control directive
 * that integrates with Angular forms.
 *
 * @stable
 */
export interface ControlValueAccessor {
    /**
     * Writes a new value to the element.
     *
     * This method will be called by the forms API to write to the view when programmatic
     * (model -> view) changes are requested.
     *
     * Example implementation of `writeValue`:
     *
     * ```ts
     * writeValue(value: any): void {
     *   this._renderer.setProperty(this._elementRef.nativeElement, 'value', value);
     * }
     * ```
     */
    writeValue(obj: any): void;
    /**
     * Registers a callback function that should be called when the control's value
     * changes in the UI.
     *
     * This is called by the forms API on initialization so it can update the form
     * model when values propagate from the view (view -> model).
     *
     * If you are implementing `registerOnChange` in your own value accessor, you
     * will typically want to save the given function so your class can call it
     * at the appropriate time.
     *
     * ```ts
     * registerOnChange(fn: (_: any) => void): void {
     *   this._onChange = fn;
     * }
     * ```
     *
     * When the value changes in the UI, your class should call the registered
     * function to allow the forms API to update itself:
     *
     * ```ts
     * host: {
     *    (change): '_onChange($event.target.value)'
     * }
     * ```
     *
     */
    registerOnChange(fn: any): void;
    /**
     * Registers a callback function that should be called when the control receives
     * a blur event.
     *
     * This is called by the forms API on initialization so it can update the form model
     * on blur.
     *
     * If you are implementing `registerOnTouched` in your own value accessor, you
     * will typically want to save the given function so your class can call it
     * when the control should be considered blurred (a.k.a. "touched").
     *
     * ```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()'
     * }
     * ```
     */
    registerOnTouched(fn: any): void;
    /**
     * This function is called by the forms API when the control status changes to
     * or from "DISABLED". Depending on the value, it should enable or disable the
     * appropriate DOM element.
     *
     * Example implementation of `setDisabledState`:
     *
     * ```ts
     * setDisabledState(isDisabled: boolean): void {
     *   this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
     * }
     * ```
     *
     * @param isDisabled
     */
    setDisabledState?(isDisabled: boolean): void;
}
/**
 * Used to provide a {@link ControlValueAccessor} for form controls.
 *
 * See {@link DefaultValueAccessor} for how to implement one.
 * @stable
 */
export declare const NG_VALUE_ACCESSOR: InjectionToken<ControlValueAccessor>;