decorator factory

Person3.ts

import { ui } from 'tabris';

function pattern(regEx: RegExp) {
  return (prototype: object, property: string) => {
    const sym = Symbol();
    Object.defineProperty(prototype, property, {
      enumerable: true,
      set(value: string) {
        if (!regEx.test(value)) {
          throw new Error(`Invalid ${property} "${value}"`);
        }
        this[sym] = value;
      },
      get() {
        return this[sym];
      }
    });
  };
}

class Person {
  @pattern(/^.+@.+\..+$/)
  public email: string;
}

const jack = new Person();

try {
  jack.email = 'jack@mail.domain'; // OK
  jack.email = 'none'; // Error: Invalid email "none"
} catch(ex) {
  console.error(ex);
} finally {
  ui.contentView.append(<textView>{jack.email}</textView>);
}