title: Error running playground. Unable to find suitable target device
body: <p>I downloaded the Swift languages's GuidedTour.playground.zip file from </p>
  
  <p><a href="https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/GuidedTour.html">https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/GuidedTour.html</a></p>
  
  <p>Unzip it as <em>GuidedTour.playground</em>,
  open it in Xcode 6.1.1, then the error message:</p>
  
  <pre><code>Error running playground.
  Unable to find suitable target device.
  </code></pre>
  
  <p>I click OK button to close the error message window,
  get back to the playground with the title "A Swift Tour". There is no output for any of the embedded code there. And every time I try to edit any of the code, the error message will pop up again and again.</p>
  
  <p>Some people on the web had the same problem and solved it by adding some devices under the menu <em>Window -> Devices -> SIMULATORS</em>. I did it, but the error keeps showing.</p>
  
  <p>If I click <em>File -> New -> Playground</em> to create a testing playground, this error message will not appear, and the testing code will run.</p>
  
  <p>A week ago, I had replaced the HDD in my Early 2008 iMac with a SSD (solid state disk), recovered the whole system to the SSD from my Time Machine backup. Everything looks good until I found out that Xcode begins to refuse to run the tutorial "A Swift Tour". Before the SSD replacement, Xcode would run it. This might be related?</p>