Swift类扩展-无法识别的选择器发送到实例

Question

When creating a class extension on a foundation class I get a unrecognized selector sent to instance when using the following:

extension NSURLSessionDataTask: Taskable {

  func isRunning() -> Bool {
    return state == .Running
  }

}

Error:

[__NSCFLocalDataTask isRunning]: unrecognized selector sent to instance 0x7fa93bdc07d0

I am trying to create a common task interface so I am able to use different kinds of classes such as operations and session tasks, is there something I am missing here?

Answer 1

Many of Cocoa classes are "class clusters", meaning you may get a different one from what you asked for. NSCFLocalDataTask is a private class and looks like it doesn't inherit from NSURLSessionDataTask . Try moving your extension to NSURLSessionTask .

Answer 2

Why this might happen: Objective-C BOOL properties starting with "is" may be handled differently. It may be that your func is exported to Objective-C as the "running" method, not as "isRunning".