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Example of building an inheritance-friendly singleton class in Swift
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| #!/usr/bin/xcrun -sdk macosx swift | |
| import Foundation | |
| public protocol SharedInstanceType | |
| { | |
| init() | |
| } | |
| private struct TokenKey | |
| { | |
| static let tokenKey = "tokenKey" | |
| } | |
| private struct InstanceKey | |
| { | |
| static let instanceKey = UnsafePointer<Void>() | |
| } | |
| private extension SharedInstanceType where Self: AnyObject | |
| { | |
| static var tokenData: NSMutableData { | |
| get { | |
| var result = objc_getAssociatedObject(self, TokenKey.tokenKey) | |
| if result == nil { | |
| result = NSMutableData(length: sizeof(dispatch_once_t)) | |
| objc_setAssociatedObject(self, TokenKey.tokenKey, result, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) | |
| } | |
| return result as! NSMutableData | |
| } | |
| } | |
| static var _instance: Self? { | |
| get { | |
| if let instance = objc_getAssociatedObject(self, InstanceKey.instanceKey), | |
| let result = instance as? Self | |
| { | |
| return result | |
| } | |
| else { | |
| return nil | |
| } | |
| } | |
| set { | |
| if let value = newValue | |
| { | |
| objc_setAssociatedObject(self, InstanceKey.instanceKey, value, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) | |
| } | |
| } | |
| } | |
| } | |
| public extension SharedInstanceType where Self: AnyObject | |
| { | |
| static var sharedInstance:Self { | |
| get { | |
| dispatch_once(UnsafeMutablePointer<dispatch_once_t>(self.tokenData.mutableBytes)) { | |
| self._instance = Self() | |
| } | |
| return _instance ?? Self() | |
| } | |
| } | |
| } | |
| class FooBar: SharedInstanceType | |
| { | |
| required init() {} | |
| } | |
| class Foo: FooBar | |
| { | |
| } | |
| class Baz: Foo | |
| { | |
| } | |
| print("\(FooBar.sharedInstance.dynamicType)") | |
| print("\(Foo.sharedInstance.dynamicType)") | |
| print("\(Baz.sharedInstance.dynamicType)") |
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Hello, Could you help in translating it to Swift 3
Thanks in advance