How do I do this?

import GameplayKit

enum FactModel {
    case Fact(String)


    func getRandomFact() -> String {

        let facts = [
            "Ants stretch when they wake up in the morning.",
            "Ostriches can run faster than horses.",
            "Olympic gold medals are actually made mostly of silver.",
            "You are born with 300 bones; by the time you are an adult you will have 206.",
            "It takes about 8 minutes for light from the Sun to reach Earth.",
            "Some bamboo plants can grow almost a meter in just one day.",
            "The state of Florida is bigger than England.",
            "Some penguins can leap 2-3 meters out of the water.",
            "On average, it takes 66 days to form a new habit.",
            "Mammoths still walked the Earth when the Great Pyramid was being built." ]

        let randomNumber = GKRandomSource.sharedRandom().nextIntWithUpperBound(facts.count)
        switch facts {
        case FactModel.Fact:
            return facts[randomNumber]
        }


    }


}