NativeScript extensions

observable-extensions.ts

import { Observable } from "data/observable";

export abstract class ObservableBase extends Observable {

  constructor() { super(); }

  public getPropertyName<PropertyName extends keyof this>(propertyName: PropertyName) { return propertyName; }
}

export function getProperty<T extends Observable, PropertyName extends keyof T>(observable: T, propertyName: PropertyName) {
  return observable.get(propertyName);
}

export function setProperty<T extends Observable, PropertyName extends keyof T>
  (observable: T, propertyName: PropertyName, propertyValue: T[PropertyName]) {
  observable.set(propertyName, propertyValue);
}

export function ObservableProperty() {
  return (target: Observable, propertyName: string) => {
    Object.defineProperty(target, propertyName, {
      get(): any {
        return this["_" + propertyName];
      },
      set(value: any): void {
        if (this["_" + propertyName] === value) { return; }

        this["_" + propertyName] = value;
        this.notifyPropertyChange(propertyName, value);
      },
      enumerable: true,
      configurable: true
    });
  };
}