NativeScript/nativescript-core/ui/core/control-state-change/index.ios.ts

/* tslint:disable:no-unused-variable */
import { ControlStateChangeListener as ControlStateChangeListenerDefinition } from '.';

class ObserverClass extends NSObject {
  // NOTE: Refactor this - use Typescript property instead of strings....
  observeValueForKeyPathOfObjectChangeContext(path: string) {
    if (path === 'selected') {
      this['_owner']._onSelectedChanged();
    } else if (path === 'enabled') {
      this['_owner']._onEnabledChanged();
    } else if (path === 'highlighted') {
      this['_owner']._onHighlightedChanged();
    }
  }
}

export class ControlStateChangeListener implements ControlStateChangeListenerDefinition {
  private _observer: NSObject;
  private _control: UIControl;
  private _observing: boolean = false;

  private _callback: (state: string) => void;

  constructor(control: UIControl, callback: (state: string) => void) {
    this._observer = ObserverClass.alloc().init();
    this._observer['_owner'] = this;
    this._control = control;
    this._callback = callback;
  }

  public start() {
    if (!this._observing) {
      this._control.addObserverForKeyPathOptionsContext(this._observer, 'highlighted', NSKeyValueObservingOptions.New, null);
      this._observing = true;
      this._updateState();
    }
  }

  public stop() {
    if (this._observing) {
      this._observing = false;
      this._control.removeObserverForKeyPath(this._observer, 'highlighted');
    }
  }

  //@ts-ignore
  private _onEnabledChanged() {
    this._updateState();
  }

  //@ts-ignore
  private _onSelectedChanged() {
    this._updateState();
  }

  //@ts-ignore
  private _onHighlightedChanged() {
    this._updateState();
  }

  private _updateState() {
    let state = 'normal';
    if (this._control.highlighted) {
      state = 'highlighted';
    }
    this._callback(state);
  }
}