请问如何给task 拓展一些属性

[WilsonScott]

我尝试 extension DownloadTask{ var platform_type: String { get { objc_getAssociatedObject(self, &Self.TYPE_KEY) as? String ?? "" } set { objc_setAssociatedObject(self, &Self.TYPE_KEY, newValue, .OBJC_ASSOCIATION_ASSIGN) } } }

结果在sessionManager.tasks 里边拿不到每个task的platform_type

[Danie1s]

extension DownloadTask{
    static var TYPE_KEY: Void?

    var platform_type: String {
        get {
            objc_getAssociatedObject(self, &Self.TYPE_KEY) as? String ?? ""
        }
        set {
            objc_setAssociatedObject(self, &Self.TYPE_KEY, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }

}

你关联对象没用好