How to save a struct, so that even when the app is closed the values don´t change?

I want to save my struct, so that the order of the items doesn´t get changed if the user closes the app. When he opens it again the order should continue, like he has never left.

Here is my code:

 struct RandomItems
    {
        var items : [String]
        var seen  = 0
        
        init(_ items:[String])
        { self.items = items }
        
        mutating func next() -> String
        {
            let index = Int(arc4random_uniform(UInt32(items.count - seen)))
            let item  = items.remove(at:index)
            items.append(item)
            seen = (seen + 1) % items.count
            return item
        }
    }