我有一个ViewController,使用关联的对象向其中添加了两个新属性:枚举和字符串(字符串版本从此处获取)
这是我的示例代码:
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"
}
}
字符串版本可以正常工作,但枚举版本却不能。我不确定是什么问题。
objc_getAssociatedObject
或的问题objc_setAssociatedObject
。get版本似乎一直都是nil,因此返回默认值One。
将您的代码更改为此
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
)
}
}
}
这样就可以了
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