从 Swift 3 转换到 Swift 4 - Void 需要 2 个参数

Question

我在 Swift 4 中遇到错误，但不太确定 Xcode 的预期结果。

这段代码:

_connection.on(method: "locationUpdate", callback: {(locationUpdate: LocationUpdate) in
      self.locationUpdateReceived(locationUpdate)
  })

产生这个错误:

Contextual closure type '([Any?], TypeConverter) -> Void' expects 2 arguments, but 1 was used in closure body

Answer 1

你可以试试

_connection.on(method: "locationUpdate", callback: { locationUpdate, other in
      self.locationUpdateReceived(locationUpdate)
  })

或

_connection.on(method: "locationUpdate") { locationUpdate, other in
   self.locationUpdateReceived(locationUpdate)
}

如果您不想使用 other 参数，最好的做法是不分配它，如下所示:

_connection.on(method: "locationUpdate") { locationUpdate, _ in
   self.locationUpdateReceived(locationUpdate)
}