title: RxJS operator for making an observable wait for a value from another observer?
body: <p>I have a situation with two observables...</p>
  <pre><code>Observable1 - an array of objects
  Observable2 - a boolean
  </code></pre>
  <p>I want to combine these so that observable1 is on activated if observable2 changes and has a boolean true value.</p>
  <p>Suggestions?</p>