Writing unity ios plugin in Swift

Is it possible to use a native Swift code as a Unity plugin?

I mean to use the code from say C# script - call its functions.

I already have a working Swift code. if its impossible, is there any workaround waybe using Objective-c as a bridge?

I think you might have to go thru Objective C to the Swift. See this:
http://stackoverflow.com/questions/24078043/call-swift-function-from-objective-c-class

This is better: