I need my app to pass the value of a variable `myVariable` from a class `firstClass` to another `secondClass` only when the variable changed its value. To do so, I thought of using the `willSet` property. Though, in Swift, you can't use it after the declaration of the variable. 

```
class firstClass: NSObject {
    var myVariable = 0

    func myFunction {
       myVariable = 5
    }
}

class secondClass: NSObject {
    var otherClass = firstClass()
    // How do I retrive the value of the variable right after its value changed?
} 

```

I also thought of adding a `NSNotification`, but that wouldn't help because it doesn't pass a value. `NSNotification` only alerts about its changes.

```
 let myVariableNotification = NSNotification(name: "myVariableNotification", object: nil)

 class firstClass: NSObject {
    var myVariable = 0

    func myFunction {
       myVariable = 5 
       notificationCenter.postNotification(myVariableNotification)
    }
}

class secondClass: NSObject {
    var otherClass = firstClass()
       NSNotificationCenter.defaultCenter().addObserverForName("myVariableNotification", 
         object: nil, 
         queue: NSOperationQueue.mainQueue()
         usingBlock: { notification in
         println("The variable has been updated!")
       })
}

```

I seem to find no way to pass a variable once that variable changed its value. How can I do that?