title: Associate slider to a Float property
body: <p>I am working on an iOS project.
  I have a <code>UISlider</code> on my ViewController.
  I want to bind a Float property (var) to the current slider value.
  If I change this property value, I want to automatically update my slider position.
  If I move my slider, I want to automatically update property value.</p>
  
  <p>I have made it work manually with delegates et stuff, but I want to know if there is a simplest way.
  In fact, I have many (very huge) UISliders, and the values can change from other part of program.</p>
  
  <p>I know in C# for example it is possible to observe a value and bind it with UI components. I want to do the same thing in swift</p>