title: Multiple Subscriptions from one Observer in Rx
body: <p>I am trying to refine the filter in my Observer over time, and I was wondering what they best way of doing this is.</p>
  
  <p>e.g. <code>myObservable.Where(x=&gt;x.Color=="red").Subscribe();</code></p>
  
  <p>and then <code>myObservable.Where(x=&gt;x.Color=="blue").Subscribe();</code></p>
  
  <p>and then merge the two into one stream so that <code>OnNext()</code> is called on Red OR Blue observables.</p>
  
  <p>Maybe it hasn't fully clicked what is going on for me.</p>
  
  <p>What if I also have <code>myObservable.Where(x=&gt;x.Type=="Car").Subscribe();</code>. It will keep calling the same OnNext() method each time? What use is this to me.. I might want to react differently depending on which subscription calls the update, but at the same time I might want to flatten the subscriptions.</p>
  
  <p>e.g. In the above scenario, if the colour is red I want to write 'new red object', and if it's a car I want to write 'new car'. How would I do this in Rx? There is an overload on the subscribe for OnNext,OnError etc.. but that requires the Observer to be an observable too (Subject).. correct me if I'm wrong.</p>
  
  <p>This makes no sense to me.. why should something that is observing changes also be observable?</p>