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Control Extension

The extension class for a Control Extension must extend the IControl interface.

The return value of the view() method can be one of the following type:

  • A subclass of a NativeScript View for Extension Control. You can design a plugin that extends the NativeScript View to have a custom native implementation for each platform. See NativeScript Building Plugins
  • A subclass of a native view (i.e. a subclass of UIView for iOS or android.view.View for Android). In the latter case, the viewIsNative() must be overridden to return true.


// MyExtensionControl.ts Example
import * as app from 'tns-core-modules/application';
import { BaseObservable } from 'mdk-core/observables/BaseObservable';
import { Color } from 'tns-core-modules/color';
import { IControl } from 'mdk-core/controls/IControl';
import { Label } from 'tns-core-modules/ui/label';

export class MyExtension extends IControl {
  private _label: any;
  private _observable: BaseObservable;
  private _value: any;

  public initialize(props) {
    if (this.definition().data.ExtensionProperties.Prop1) {
      this._value = this.definition().data.ExtensionProperties.Prop1.Value;
    else {
      this._value = "Default Value";
    const color = new Color('gray');
    this._label = new Label();
    this._label.backgroundColor = color;

  public view() {
    //Use provided ValueResolver to resolve value to support bindings, rules, etc in your extension
    this.valueResolver().resolveValue(this._value).then((resolvedValue)=> {
      this._label.text = resolvedValue;
    return this._label;

  public viewIsNative() {
    return true;

  public observable() {
    if (!this._observable) {
      this._observable = new BaseObservable(this, this.definition(),;
    return this._observable;

  public setValue(value: any, notify: boolean): Promise<any> {
    this._value = value;
    this._label.text = value;
    return Promise.resolve();

  public setContainer(container: IControl) {
    // do nothing

  get isBindable(): boolean {
    return true;

  public bind(): Promise<any> {
    return this.observable().bindValue(this._value);

Last update: August 12, 2020