Associated Object Support for Swift 2.3

This is your AssociatedObjectSupport.swift. It's for Swift 2.3 and it's based on this. It can handles nulls, and non-objects, too (by wrapping them in Lifted).
import UIKit

final class Lifted {
    let value: Any
    init(_ x: Any) {
        value = x
    }
}

extension NSObject {
    func setAssociatedObject(value: T, associativeKey: UnsafePointer<Void>, policy: objc_AssociationPolicy = .OBJC_ASSOCIATION_RETAIN_NONATOMIC) {
        if let v: AnyObject = value as? AnyObject {
            objc_setAssociatedObject(self, associativeKey, v,  policy)
        }
        else {
            let liftedObject = Lifted(value)
            objc_setAssociatedObject(self, associativeKey, liftedObject,  policy)
        }
    }
    
    func getAssociatedObject(associativeKey: UnsafePointer<Void>) -> T? {
        let value = objc_getAssociatedObject(self, associativeKey)
        if let value = value as? Lifted {
            return value.value as? T
        }
        return value as? T
    }
}
Example UIView Extension
And here's an example extension to UIView that uses it. Note the clever use of a private struct to get static variables on the Extension nicely.
extension UIView {    
    private struct AssociatedKeys {
        static var viewExtension = "viewExtension"
        static var anotherView = "someOtherView"
        static var someFloat = "someFloat"
    }
        
    var someFloat: Float {
        get {
            return getAssociatedObject(&AssociatedKeys.someFloat) ?? 0.0
        }
        set {
            setAssociatedObject(newValue, associativeKey: &AssociatedKeys.someFloat)
        }
    }
    
    var baseTransform: CGAffineTransform? {
        get {
            return getAssociatedObject(&AssociatedKeys.viewExtension)
        }
        set {
            setAssociatedObject(newValue, associativeKey: &AssociatedKeys.viewExtension)
        }
    }
    
    var anotherView: UIView? {
        get {
            return getAssociatedObject(&AssociatedKeys.anotherView)
        }
        
        set {
            setAssociatedObject(newValue, associativeKey: &AssociatedKeys.anotherView)
        }
    }
}


Using the Example
var view = UIView()
view.baseTransform = CGAffineTransformIdentity
print("what's up \(view.baseTransform)")
view.baseTransform = nil
print("what's up \(view.baseTransform == nil)")
view.anotherView = UIView()
print("you got another view? \(view.anotherView)   \(view.anotherView?.anotherView)")
view.anotherView = nil
view.someFloat = 32.5
print("what's it? \(view.someFloat)")