observer-locator.js

observer-locator.js

import { ObserverLocator } from 'aurelia-binding';
import { inject } from 'aurelia-dependency-injection';

@inject(ObserverLocator)
export class App {
  constructor(observerLocator) {
    this.subscription = observerLocator.getObserver(this, 'selectedValue');
    this.subscription.subscribe(this.selectedValueChanged);
  }
  detached() {
    this.subscription.unsubscribe();
  }
  
  selectedValue = '';
  selectedValueChanged(newValue) {
    console.log('select changed', newValue);
  }
  setSelectedValue() {
    this.selectedValue = 'ny2';
  }
}

Better use the bindingEngine
http://stackoverflow.com/questions/28419242/property-change-subscription-with-aurelia/28437456#28437456