objective-c - 将 swift 的 "forced downcast(as!)"转换为 objective-c

Question

我想将这条 swift 代码转换为 Objective-C

let location = CLLocationCoordinate2D(latitude: (marker.userData as! location).lat, longitude: (marker.userData as! location).lon)

userData 是 id 类型，它被强制向下转换为 location 但是当我尝试在 Objective-C 中转换 userData 时，我得到这个:

Multiple methods named 'location' found with mismatched result, parameter type or attributes

这是我的代码:

struct CLLocationCoordinate2D markerLocation;
    markerLocation.longitude=[(CLLocation *)[marker.userData location] coordinate].longitude;

Answer 1

你想转换 userData，而不是 location 消息的结果。

markerLocation.longitude=[(CLLocation *)[marker.userData location] coordinate].longitude;

……应该是……

markerLocation.longitude=[(CLLocation *)(marker.userData) coordinate].longitude;