title: How do I update a progress bar using NSProgress using Cocoa Bindings?
body: <p>I've been trying to use the new NSProgress class to report the progress of an operation in my Mac app. Right now, it's saved as a property in my App Delegate (and is updated from a different class and a different queue), and seems to be updated correctly, as proven by logging <code>[_currentProgress fractionCompleted]</code>.</p>
  
  <p>However, my issues come when I try to update a progress bar using the NSProgress object. I've got the progress bar set up with bindings something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/ICben.png" alt="Binding Screenshot"></p>
  
  <p>The progress bar seems to stay on whatever my null placeholder is (as proven by changing the null placeholder to '1'), not redrawing or updating to accommodate any further progress. <code>currentProgress</code> is only set once an operation has started, which will be why the progress bar uses the null placeholder at first, but it makes no effort to update the progress bar when an NSProgress object is set to that property.</p>
  
  <p>It'd be great if somebody could help me out here… (There must be something stupid I'm doing wrong!)</p>