Swift is built with Objective-C interoperability in mind. All of the Objective-C Foundation classes are available in Swift, and they've done their best to mitigate the differences in software design.

However, learning Swift without first learning how the underlying Objective-C libraries work, the design patterns, the available functions, Swift-Objective-C-Interop is going to be very difficult.

I'd recommend learning Swift and Objective-C at the same time. If you learn how to do something in Swift, learn how to do it in Objective-C. Objective-C isn't going anywhere, any time soon.