docs(forms): update API reference for value accessors (#26946)

PR Close #26946

packages/forms/src/directives/checkbox_value_accessor.ts

@@ -17,17 +17,26 @@ export const CHECKBOX_VALUE_ACCESSOR: any = {
 };
 
 /**
- * The accessor for writing a value and listening to changes on a checkbox input element.
+ * @description
+ * A `ControlValueAccessor` for writing a value and listening to changes on a checkbox input
+ * element.
  *
  * @usageNotes
- * ### Example
  *
- * ```
+ * ### Using a checkbox with a reactive form.
- * <input type="checkbox" name="rememberLogin" ngModel>
+ *
+ * The following example shows how to use a checkbox with a reactive form.
+ *
+ * ```ts
+ * const rememberLoginControl = new FormControl();
+ * ```
+ *
+ * ```
+ * <input type="checkbox" [formControl]="rememberLoginControl">
  * ```
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  * @publicApi
  */
 @Directive({
@@ -37,17 +46,50 @@ export const CHECKBOX_VALUE_ACCESSOR: any = {
   providers: [CHECKBOX_VALUE_ACCESSOR]
 })
 export class CheckboxControlValueAccessor implements ControlValueAccessor {
+  /**
+   * @description
+   * The registered callback function called when a change event occurs on the input element.
+   */
   onChange = (_: any) => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
   constructor(private _renderer: Renderer2, private _elementRef: ElementRef) {}
 
+  /**
+   * Sets the "checked" property on the input element.
+   *
+   * @param value The checked value
+   */
   writeValue(value: any): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'checked', value);
   }
+
+  /**
+   * @description
+   * Registers a function called when the control value changes.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (_: any) => {}): void { this.onChange = fn; }
+
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => {}): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }

packages/forms/src/directives/default_value_accessor.ts

@@ -32,18 +32,28 @@ function _isAndroid(): boolean {
 export const COMPOSITION_BUFFER_MODE = new InjectionToken<boolean>('CompositionEventMode');
 
 /**
- * The default accessor for writing a value and listening to changes that is used by the
+ * @description
- * `NgModel`, `FormControlDirective`, and `FormControlName` directives.
+ * The default `ControlValueAccessor` for writing a value and listening to changes on input
+ * elements. The accessor is used by the `FormControlDirective`, `FormControlName`, and
+ * `NgModel` directives.
  *
  * @usageNotes
- * ### Example
  *
- * ```
+ * ### Using the default value accessor
- * <input type="text" name="searchQuery" ngModel>
+ *
+ * The following example shows how to use an input element that activates the default value accessor
+ * (in this case, a text field).
+ *
+ * ```ts
+ * const firstNameControl = new FormControl();
+ * ```
+ *
+ * ```
+ * <input type="text" [formControl]="firstNameControl">
  * ```
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  * @publicApi
  */
 @Directive({
@@ -61,7 +71,16 @@ export const COMPOSITION_BUFFER_MODE = new InjectionToken<boolean>('CompositionE
   providers: [DEFAULT_VALUE_ACCESSOR]
 })
 export class DefaultValueAccessor implements ControlValueAccessor {
+  /**
+   * @description
+   * The registered callback function called when an input event occurs on the input element.
+   */
   onChange = (_: any) => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
   /** Whether the user is creating a composition string (IME events). */
@@ -75,14 +94,37 @@ export class DefaultValueAccessor implements ControlValueAccessor {
     }
   }
 
+  /**
+   * Sets the "value" property on the input element.
+   *
+   * @param value The checked value
+   */
   writeValue(value: any): void {
     const normalizedValue = value == null ? '' : value;
     this._renderer.setProperty(this._elementRef.nativeElement, 'value', normalizedValue);
   }
 
+  /**
+   * @description
+   * Registers a function called when the control value changes.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (_: any) => void): void { this.onChange = fn; }
+
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => void): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }

packages/forms/src/directives/number_value_accessor.ts

@@ -17,18 +17,27 @@ export const NUMBER_VALUE_ACCESSOR: any = {
 };
 
 /**
- * The accessor for writing a number value and listening to changes that is used by the
+ * @description
- * `NgModel`, `FormControlDirective`, and `FormControlName` directives.
+ * The `ControlValueAccessor` for writing a number value and listening to number input changes.
+ * The value accessor is used by the `FormControlDirective`, `FormControlName`, and  `NgModel`
+ * directives.
  *
  * @usageNotes
- * ### Example
  *
- * ```
+ * ### Using a number input with a reactive form.
- * <input type="number" [(ngModel)]="age">
+ *
+ * The following example shows how to use a number input with a reactive form.
+ *
+ * ```ts
+ * const totalCountControl = new FormControl();
+ * ```
+ *
+ * ```
+ * <input type="number" [formControl]="totalCountControl">
  * ```
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  */
 @Directive({
   selector:
@@ -41,22 +50,55 @@ export const NUMBER_VALUE_ACCESSOR: any = {
   providers: [NUMBER_VALUE_ACCESSOR]
 })
 export class NumberValueAccessor implements ControlValueAccessor {
+  /**
+   * @description
+   * The registered callback function called when a change or input event occurs on the input
+   * element.
+   */
   onChange = (_: any) => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
   constructor(private _renderer: Renderer2, private _elementRef: ElementRef) {}
 
+  /**
+   * Sets the "value" property on the input element.
+   *
+   * @param value The checked value
+   */
   writeValue(value: number): void {
     // The value needs to be normalized for IE9, otherwise it is set to 'null' when null
     const normalizedValue = value == null ? '' : value;
     this._renderer.setProperty(this._elementRef.nativeElement, 'value', normalizedValue);
   }
 
+  /**
+   * @description
+   * Registers a function called when the control value changes.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (_: number|null) => void): void {
     this.onChange = (value) => { fn(value == '' ? null : parseFloat(value)); };
   }
+
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => void): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }

packages/forms/src/directives/radio_control_value_accessor.ts

@@ -18,16 +18,25 @@ export const RADIO_VALUE_ACCESSOR: any = {
 };
 
 /**
- * Internal class used by Angular to uncheck radio buttons with the matching name.
+ * @description
+ * Class used by Angular to track radio buttons. For internal use only.
  */
 @Injectable()
 export class RadioControlRegistry {
   private _accessors: any[] = [];
 
+  /**
+   * @description
+   * Adds a control to the internal registry. For internal use only.
+   */
   add(control: NgControl, accessor: RadioControlValueAccessor) {
     this._accessors.push([control, accessor]);
   }
 
+  /**
+   * @description
+   * Removes a control from the internal registry. For internal use only.
+   */
   remove(accessor: RadioControlValueAccessor) {
     for (let i = this._accessors.length - 1; i >= 0; --i) {
       if (this._accessors[i][1] === accessor) {
@@ -37,6 +46,10 @@ export class RadioControlRegistry {
     }
   }
 
+  /**
+   * @description
+   * Selects a radio button. For internal use only.
+   */
   select(accessor: RadioControlValueAccessor) {
     this._accessors.forEach((c) => {
       if (this._isSameGroup(c, accessor) && c[1] !== accessor) {
@@ -56,32 +69,22 @@ export class RadioControlRegistry {
 
 /**
  * @description
- *
+ * The `ControlValueAccessor` for writing radio control values and listening to radio control
- * Writes radio control values and listens to radio control changes.
+ * changes. The value accessor is used by the `FormControlDirective`, `FormControlName`, and
- *
+ * `NgModel` directives.
- * Used by `NgModel`, `FormControlDirective`, and `FormControlName`
- * to keep the view synced with the `FormControl` model.
- *
- * If you have imported the `FormsModule` or the `ReactiveFormsModule`, this
- * value accessor will be active on any radio control that has a form directive. You do
- * **not** need to add a special selector to activate it.
  *
  * @usageNotes
- * ### How to use radio buttons with form directives
  *
- * To use radio buttons in a template-driven form, you'll want to ensure that radio buttons
+ * ### Using radio buttons with reactive form directives
- * in the same group have the same `name` attribute.  Radio buttons with different `name`
- * attributes do not affect each other.
  *
- * {@example forms/ts/radioButtons/radio_button_example.ts region='TemplateDriven'}
+ * The follow example shows how to use radio buttons in a reactive form. When using radio buttons in
- *
+ * a reactive form, radio buttons in the same group should have the same `formControlName`.
- * When using radio buttons in a reactive form, radio buttons in the same group should have the
+ * Providing a `name` attribute is optional.
- * same `formControlName`. You can also add a `name` attribute, but it's optional.
  *
  * {@example forms/ts/reactiveRadioButtons/reactive_radio_button_example.ts region='Reactive'}
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  * @publicApi
  */
 @Directive({
@@ -101,32 +104,81 @@ export class RadioControlValueAccessor implements ControlValueAccessor,
   /** @internal */
   // TODO(issue/24571): remove '!'.
   _fn !: Function;
+
+  /**
+   * @description
+   * The registered callback function called when a change event occurs on the input element.
+   */
   onChange = () => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
+  /**
+   * @description
+   * Tracks the name of the radio input element.
+   */
   // TODO(issue/24571): remove '!'.
   @Input() name !: string;
+
+  /**
+   * @description
+   * Tracks the name of the `FormControl` bound to the directive. The name corresponds
+   * to a key in the parent `FormGroup` or `FormArray`.
+   */
   // TODO(issue/24571): remove '!'.
   @Input() formControlName !: string;
+
+  /**
+   * @description
+   * Tracks the value of the radio input element
+   */
   @Input() value: any;
 
   constructor(
       private _renderer: Renderer2, private _elementRef: ElementRef,
       private _registry: RadioControlRegistry, private _injector: Injector) {}
 
+  /**
+   * @description
+   * A lifecycle method called when the directive is initialized. For internal use only.
+   *
+   * @param changes A object of key/value pairs for the set of changed inputs.
+   */
   ngOnInit(): void {
     this._control = this._injector.get(NgControl);
     this._checkName();
     this._registry.add(this._control, this);
   }
 
+  /**
+   * @description
+   * Lifecycle method called before the directive's instance is destroyed. For internal use only.
+   *
+   * @param changes A object of key/value pairs for the set of changed inputs.
+   */
   ngOnDestroy(): void { this._registry.remove(this); }
 
+  /**
+   * @description
+   * Sets the "checked" property value on the radio input element.
+   *
+   * @param value The checked value
+   */
   writeValue(value: any): void {
     this._state = value === this.value;
     this._renderer.setProperty(this._elementRef.nativeElement, 'checked', this._state);
   }
 
+  /**
+   * @description
+   * Registers a function called when the control value changes.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (_: any) => {}): void {
     this._fn = fn;
     this.onChange = () => {
@@ -135,10 +187,26 @@ export class RadioControlValueAccessor implements ControlValueAccessor,
     };
   }
 
+  /**
+   * Sets the "value" on the radio input element and unchecks it.
+   *
+   * @param value
+   */
   fireUncheck(value: any): void { this.writeValue(value); }
 
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => {}): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }

packages/forms/src/directives/range_value_accessor.ts

@@ -17,18 +17,27 @@ export const RANGE_VALUE_ACCESSOR: StaticProvider = {
 };
 
 /**
- * The accessor for writing a range value and listening to changes that is used by the
+ * @description
- * `NgModel`, `FormControlDirective`, and `FormControlName` directives.
+ * The `ControlValueAccessor` for writing a range value and listening to range input changes.
+ * The value accessor is used by the `FormControlDirective`, `FormControlName`, and  `NgModel`
+ * directives.
  *
  * @usageNotes
- * ### Example
  *
- * ```
+ * ### Using a range input with a reactive form
- * <input type="range" [(ngModel)]="age" >
+ *
+ * The following example shows how to use a range input with a reactive form.
+ *
+ * ```ts
+ * const ageControl = new FormControl();
+ * ```
+ *
+ * ```
+ * <input type="range" [formControl]="ageControl">
  * ```
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  */
 @Directive({
   selector:
@@ -41,21 +50,53 @@ export const RANGE_VALUE_ACCESSOR: StaticProvider = {
   providers: [RANGE_VALUE_ACCESSOR]
 })
 export class RangeValueAccessor implements ControlValueAccessor {
+  /**
+   * @description
+   * The registered callback function called when a change or input event occurs on the input
+   * element.
+   */
   onChange = (_: any) => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
   constructor(private _renderer: Renderer2, private _elementRef: ElementRef) {}
 
+  /**
+   * Sets the "value" property on the input element.
+   *
+   * @param value The checked value
+   */
   writeValue(value: any): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'value', parseFloat(value));
   }
 
+  /**
+   * @description
+   * Registers a function called when the control value changes.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (_: number|null) => void): void {
     this.onChange = (value) => { fn(value == '' ? null : parseFloat(value)); };
   }
 
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => void): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the range input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }

packages/forms/src/directives/select_control_value_accessor.ts

@@ -28,35 +28,26 @@ function _extractId(valueString: string): string {
 
 /**
  * @description
- *
+ * The `ControlValueAccessor` for writing select control values and listening to select control
- * Writes values and listens to changes on a select element.
+ * changes. The value accessor is used by the `FormControlDirective`, `FormControlName`, and
- *
+ * `NgModel` directives.
- * Used by `NgModel`, `FormControlDirective`, and `FormControlName`
- * to keep the view synced with the `FormControl` model.
- *
- * If you have imported the `FormsModule` or the `ReactiveFormsModule`, this
- * value accessor will be active on any select control that has a form directive. You do
- * **not** need to add a special selector to activate it.
  *
  * @usageNotes
- * ### How to use select controls with form directives
+ *
+ * ### Using select controls in a reactive form
+ *
+ * The following examples show how to use a select control in a reactive form.
+ *
+ * {@example forms/ts/reactiveSelectControl/reactive_select_control_example.ts region='Component'}
+ *
+ * ### Using select controls in a template-driven form
  *
  * To use a select in a template-driven form, simply add an `ngModel` and a `name`
  * attribute to the main `<select>` tag.
  *
- * If your option values are simple strings, you can bind to the normal `value` property
- * on the option.  If your option values happen to be objects (and you'd like to save the
- * selection in your form as an object), use `ngValue` instead:
- *
  * {@example forms/ts/selectControl/select_control_example.ts region='Component'}
  *
- * In reactive forms, you'll also want to add your form directive (`formControlName` or
+ * ### Customizing option selection
- * `formControl`) on the main `<select>` tag. Like in the former example, you have the
- * choice of binding to the  `value` or `ngValue` property on the select's options.
- *
- * {@example forms/ts/reactiveSelectControl/reactive_select_control_example.ts region='Component'}
- *
- * ### Caveat: Option selection
  *
  * Angular uses object identity to select option. It's possible for the identities of items
  * to change while the data does not. This can happen, for example, if the items are produced
@@ -67,10 +58,12 @@ function _extractId(valueString: string): string {
  * `compareWith` takes a **function** which has two arguments: `option1` and `option2`.
  * If `compareWith` is given, Angular selects option by the return value of the function.
  *
- * ### Syntax
+ * ```ts
+ * const selectedCountriesControl = new FormControl();
+ * ```
  *
  * ```
- * <select [compareWith]="compareFn"  [(ngModel)]="selectedCountries">
+ * <select [compareWith]="compareFn"  [formControl]="selectedCountriesControl">
  *     <option *ngFor="let country of countries" [ngValue]="country">
  *         {{country.name}}
  *     </option>
@@ -81,13 +74,13 @@ function _extractId(valueString: string): string {
  * }
  * ```
  *
- * Note: We listen to the 'change' event because 'input' events aren't fired
+ * **Note:** We listen to the 'change' event because 'input' events aren't fired
  * for selects in Firefox and IE:
  * https://bugzilla.mozilla.org/show_bug.cgi?id=1024350
  * https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/4660045/
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  * @publicApi
  */
 @Directive({
@@ -103,9 +96,23 @@ export class SelectControlValueAccessor implements ControlValueAccessor {
   /** @internal */
   _idCounter: number = 0;
 
+  /**
+   * @description
+   * The registered callback function called when a change event occurs on the input element.
+   */
   onChange = (_: any) => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
+  /**
+   * @description
+   * Tracks the option comparison algorithm for tracking identities when
+   * checking for changes.
+   */
   @Input()
   set compareWith(fn: (o1: any, o2: any) => boolean) {
     if (typeof fn !== 'function') {
@@ -118,6 +125,12 @@ export class SelectControlValueAccessor implements ControlValueAccessor {
 
   constructor(private _renderer: Renderer2, private _elementRef: ElementRef) {}
 
+  /**
+   * Sets the "value" property on the input element. The "selectedIndex"
+   * property is also set if an ID is provided on the option element.
+   *
+   * @param value The checked value
+   */
   writeValue(value: any): void {
     this.value = value;
     const id: string|null = this._getOptionId(value);
@@ -128,14 +141,32 @@ export class SelectControlValueAccessor implements ControlValueAccessor {
     this._renderer.setProperty(this._elementRef.nativeElement, 'value', valueString);
   }
 
+  /**
+   * @description
+   * Registers a function called when the control value changes.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (value: any) => any): void {
     this.onChange = (valueString: string) => {
       this.value = this._getOptionValue(valueString);
       fn(this.value);
     };
   }
+
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => any): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the select input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }
@@ -160,17 +191,20 @@ export class SelectControlValueAccessor implements ControlValueAccessor {
 
 /**
  * @description
- *
  * Marks `<option>` as dynamic, so Angular can be notified when options change.
  *
- * See docs for `SelectControlValueAccessor` for usage examples.
+ * @see `SelectControlValueAccessor`
  *
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
  * @publicApi
  */
 @Directive({selector: 'option'})
 export class NgSelectOption implements OnDestroy {
+  /**
+   * @description
+   * ID of the option element
+   */
   // TODO(issue/24571): remove '!'.
   id !: string;
 
@@ -180,6 +214,11 @@ export class NgSelectOption implements OnDestroy {
     if (this._select) this.id = this._select._registerOption();
   }
 
+  /**
+   * @description
+   * Tracks the value bound to the option element. Unlike the value binding,
+   * ngValue supports binding to objects.
+   */
   @Input('ngValue')
   set ngValue(value: any) {
     if (this._select == null) return;
@@ -188,6 +227,11 @@ export class NgSelectOption implements OnDestroy {
     this._select.writeValue(this._select.value);
   }
 
+  /**
+   * @description
+   * Tracks simple string values bound to the option element.
+   * For objects, use the `ngValue` input binding.
+   */
   @Input('value')
   set value(value: any) {
     this._setElementValue(value);
@@ -199,6 +243,10 @@ export class NgSelectOption implements OnDestroy {
     this._renderer.setProperty(this._element.nativeElement, 'value', value);
   }
 
+  /**
+   * @description
+   * Lifecycle method called before the directive's instance is destroyed. For internal use only.
+   */
   ngOnDestroy(): void {
     if (this._select) {
       this._select._optionMap.delete(this.id);

packages/forms/src/directives/select_multiple_control_value_accessor.ts

@@ -41,34 +41,36 @@ abstract class HTMLCollection {
 }
 
 /**
- * The accessor for writing a value and listening to changes on a select element.
+ * @description
+ * The `ControlValueAccessor` for writing multi-select control values and listening to multi-select control
+ * changes. The value accessor is used by the `FormControlDirective`, `FormControlName`, and `NgModel`
+ * directives.
+ * 
+ * @see `SelectControlValueAccessor`
  *
  * @usageNotes
- * ### Caveat: Options selection
  * 
- * Angular uses object identity to select options. It's possible for the identities of items
+ * ### Using a multi-select control
- * to change while the data does not. This can happen, for example, if the items are produced
- * from an RPC to the server, and that RPC is re-run. Even if the data hasn't changed, the
- * second response will produce objects with different identities.
  * 
- * To customize the default option comparison algorithm, `<select multiple>` supports `compareWith`
+ * The follow example shows you how to use a multi-select control with a reactive form.
- * input. `compareWith` takes a **function** which has two arguments: `option1` and `option2`.
- * If `compareWith` is given, Angular selects options by the return value of the function.
  * 
- * ### Syntax
+ * ```ts
+ * const countryControl = new FormControl();
+ * ```
  *
  * ```
- * <select multiple [compareWith]="compareFn"  [(ngModel)]="selectedCountries">
+ * <select multiple name="countries" [formControl]="countryControl">
- *     <option *ngFor="let country of countries" [ngValue]="country">
+ *   <option *ngFor="let country of countries" [ngValue]="country">
- *         {{country.name}}
+ *     {{ country.name }}
- *     </option>
+ *   </option>
  * </select>
- *
- * compareFn(c1: Country, c2: Country): boolean {
- *     return c1 && c2 ? c1.id === c2.id : c1 === c2;
- * }
  * ```
  * 
+ * ### Customizing option selection
+ *  
+ * To customize the default option comparison algorithm, `<select>` supports `compareWith` input.
+ * See the `SelectControlValueAccessor` for usage.
+ *
  * @ngModule ReactiveFormsModule
  * @ngModule FormsModule
  * @publicApi
@@ -80,15 +82,34 @@ abstract class HTMLCollection {
   providers: [SELECT_MULTIPLE_VALUE_ACCESSOR]
 })
 export class SelectMultipleControlValueAccessor implements ControlValueAccessor {
+  /**
+   * @description
+   * The current value
+   */
   value: any;
+
   /** @internal */
   _optionMap: Map<string, NgSelectMultipleOption> = new Map<string, NgSelectMultipleOption>();
   /** @internal */
   _idCounter: number = 0;
 
+  /**
+   * @description
+   * The registered callback function called when a change event occurs on the input element.
+   */
   onChange = (_: any) => {};
+
+  /**
+   * @description
+   * The registered callback function called when a blur event occurs on the input element.
+   */
   onTouched = () => {};
 
+  /**
+   * @description
+   * Tracks the option comparison algorithm for tracking identities when
+   * checking for changes.
+   */
   @Input()
   set compareWith(fn: (o1: any, o2: any) => boolean) {
     if (typeof fn !== 'function') {
@@ -101,6 +122,13 @@ export class SelectMultipleControlValueAccessor implements ControlValueAccessor
 
   constructor(private _renderer: Renderer2, private _elementRef: ElementRef) {}
 
+  /**
+   * @description
+   * Sets the "value" property on one or of more
+   * of the select's options.
+   *
+   * @param value The value
+   */
   writeValue(value: any): void {
     this.value = value;
     let optionSelectedStateSetter: (opt: NgSelectMultipleOption, o: any) => void;
@@ -114,6 +142,13 @@ export class SelectMultipleControlValueAccessor implements ControlValueAccessor
     this._optionMap.forEach(optionSelectedStateSetter);
   }
 
+  /**
+   * @description
+   * Registers a function called when the control value changes
+   * and writes an array of the selected options.
+   *
+   * @param fn The callback function
+   */
   registerOnChange(fn: (value: any) => any): void {
     this.onChange = (_: any) => {
       const selected: Array<any> = [];
@@ -140,8 +175,20 @@ export class SelectMultipleControlValueAccessor implements ControlValueAccessor
       fn(selected);
     };
   }
+
+  /**
+   * @description
+   * Registers a function called when the control is touched.
+   *
+   * @param fn The callback function
+   */
   registerOnTouched(fn: () => any): void { this.onTouched = fn; }
 
+  /**
+   * Sets the "disabled" property on the select input element.
+   *
+   * @param isDisabled The disabled value
+   */
   setDisabledState(isDisabled: boolean): void {
     this._renderer.setProperty(this._elementRef.nativeElement, 'disabled', isDisabled);
   }
@@ -169,18 +216,14 @@ export class SelectMultipleControlValueAccessor implements ControlValueAccessor
 }
 
 /**
+ * @description
  * Marks `<option>` as dynamic, so Angular can be notified when options change.
  *
- * @usageNotes
+ * @see `SelectMultipleControlValueAccessor`
- * ### Example
  *
- * ```
- * <select multiple name="city" ngModel>
- *   <option *ngFor="let c of cities" [value]="c"></option>
- * </select>
- * ```
- * @ngModule FormsModule
  * @ngModule ReactiveFormsModule
+ * @ngModule FormsModule
+ * @publicApi
  */
 @Directive({selector: 'option'})
 export class NgSelectMultipleOption implements OnDestroy {
@@ -197,6 +240,11 @@ export class NgSelectMultipleOption implements OnDestroy {
     }
   }
 
+  /**
+   * @description
+   * Tracks the value bound to the option element. Unlike the value binding,
+   * ngValue supports binding to objects.
+   */
   @Input('ngValue')
   set ngValue(value: any) {
     if (this._select == null) return;
@@ -205,6 +253,11 @@ export class NgSelectMultipleOption implements OnDestroy {
     this._select.writeValue(this._select.value);
   }
 
+  /**
+   * @description
+   * Tracks simple string values bound to the option element.
+   * For objects, use the `ngValue` input binding.
+   */
   @Input('value')
   set value(value: any) {
     if (this._select) {
@@ -226,6 +279,10 @@ export class NgSelectMultipleOption implements OnDestroy {
     this._renderer.setProperty(this._element.nativeElement, 'selected', selected);
   }
 
+  /**
+   * @description
+   * Lifecycle method called before the directive's instance is destroyed. For internal use only.
+   */
   ngOnDestroy(): void {
     if (this._select) {
       this._select._optionMap.delete(this.id);