I have a ViewController to which I added two new properties using associated objects: an enum and a string (string version is taken from here)
Here is my example code:
extension UIViewController {
private struct AssociatedKeys {
static var handle = "handle"
}
enum CustomStringEnum: String {
case One = "One"
case Two = "Two"
case Three = "Three"
}
var customEnum: CustomStringEnum {
get {
return objc_getAssociatedObject(self, &AssociatedKeys.handle) as? CustomStringEnum ?? .One
}
set {
objc_setAssociatedObject(self, &AssociatedKeys.handle, newValue.rawValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
}
var descriptiveName: String {
get {
return objc_getAssociatedObject(self, &AssociatedKeys.handle) as! String
}
set {
objc_setAssociatedObject(
self,
&AssociatedKeys.handle,
newValue as NSString?,
.OBJC_ASSOCIATION_RETAIN_NONATOMIC
)
}
}
}
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let vc = UIViewController()
vc.customEnum = .Three
vc.descriptiveName = "Three"
print(vc.customEnum.rawValue) // -> This prints "One"
print(vc.descriptiveName) // -> This prints "Three"
}
}
The string version its working correctly, but the enum one doesn't. And I am not sure what the problem is.
It is a problem with the objc_getAssociatedObject
or the objc_setAssociatedObject
. The get version seems to be nil all the time, so the default value of One is returned.
Change your code to this
extension UIViewController {
private struct AssociatedKeys {
static var handle = "handle"
static var enumContext = "enumContext"
}
enum CustomStringEnum: String {
case One = "One"
case Two = "Two"
case Three = "Three"
}
var customEnum: CustomStringEnum {
get {
let rawvalue = objc_getAssociatedObject(self, &AssociatedKeys.enumContext)
if rawvalue == nil{
return .One
}else{
return CustomStringEnum(rawValue: rawvalue as! String)!;
}
}
set {
objc_setAssociatedObject(self, &AssociatedKeys.enumContext, newValue.rawValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
}
var descriptiveName: String {
get {
return objc_getAssociatedObject(self, &AssociatedKeys.handle) as! String
}
set {
objc_setAssociatedObject(
self,
&AssociatedKeys.handle,
newValue as NSString?,
.OBJC_ASSOCIATION_RETAIN_NONATOMIC
)
}
}
}
Then it will work