Question 130455 in Xcode Question posted in
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Xcode – Simplify my code for Searching and Replacing Strings in an Array

I’m would like to get some help wrapping my head around simplifying this code. This works but I’m thinking there Must be a simpler way.

Goal:

  1. Replace all VirtualRide w/ Ride
  2. If Both VirtualRide and Ride exists in array, remove VirtualRide

eg:

input = ["Ride", "VirtualRide", "Run", "VirtualRun"]  expected output = ["Ride", "Run"]
input = ["VirtualRide", "VirtualRun"]                 expected output = ["Ride", "Run"]
input = ["Ride", "Run"]                               expected output = ["Ride", "Run"] (Basically do nothing)

This is the current code that works, but is just seems ugly and long.

let sportsArray = ["Ride", "VirtualRide"]
var newSportsArray = sportsArray // sportsArray is passed in. So it's a Let

 let ixVirtualRide = sportsArray.firstIndex(of: "VirtualRide")
if let ixVirtualRide = ixVirtualRide {
  
  if newSportsArray.filter({$0.contains("Ride")}).count > 1 {
    newSportsArray.remove(at: ixVirtualRide)
  }
  
  
  if newSportsArray.filter({$0.contains("VirtualRide")}).count == 1 {
    newSportsArray.remove(at: ixVirtualRide)
    newSportsArray.append("Ride")
  }
}
Tags:

3

Answers


  1. 0

    If the goal is to remove any Virtual occurrence, delete the substring if matched:

    sportsArray = sportsArray.map{$0.contains("Virtual") ? $0.replacingOccurrences(of: "Virtual", with: "") : $0}

    Then, if the array cannot contain anything else than those four elements, use a set to clear duplicates:

    let unique = Array(Set(sportsArray))
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  2. 0

    Here we import OrderedCollections from the Swift package library because we want to use an Ordered set to remove duplicates but maintain order:

    import OrderedCollections

    If Virtual isn’t always at the start, and never appears anywhere else, you can use replacingOccurrences(of:) otherwise a handy extension on String helps here:

    extension String {
    func deletingPrefix(_ prefix: String) -> String {
        guard hasPrefix(prefix) else { return self }
        return String(dropFirst(prefix.count))
    }
}

    Now we can make a function that takes the array of strings and removes the prefixes and deduplicates the results, maintaining the order of them.

    func f(_ s: [String]) -> [String] {
    Array(OrderedSet(s.map { $0.deletingPrefix("Virtual") }))
}

    Then

    f(["Ride", "VirtualRide", "Run", "VirtualRun"] // = ["Ride", "Run"]

    etc for all your example inputs.

    If you prefer this style you can write it like this too:

    func makePrefixDeleter(_ p: String) -> (String) -> String {
    return { str in
        str.deletingPrefix(p)
    }
}

let deleteVirtualPrefix = makePrefixDeleter("Virtual")

func f(_ s: [String]) -> [String] {
    Array(OrderedSet(s.map(deleteVirtualPrefix)))
}

    Which might be handy if you have a use for the "Virtual" prefix deleter function in other places.

    The other approach that suggests itself is to standardise your input via an enum (essentially parsing it), like:

    enum Thing {
    case ride
    case run

    init?(_ s: String) {
        switch s {
        case "Ride", "VirtualRide":
            self = .ride
        case "Run", "VirtualRun":
            self = .run
        default:
            return nil
        }
    }

    var str: String {
        switch self {
        case .ride: return "Ride"
        case .run: return "Run"
        }
    }
}

let example = OrderedSet(["Ride", "VirtualRide", "Run", "VirtualRun"].compactMap(Thing.init(_:)).map(.str)))
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  3. 0

    Your specifications are incomplete and don’t match your examples. I guess you want to

    1. remove the prefix Virtual
    2. remove duplicates (e.g. drop the Ride from VirtualRide if there is another Ride)
    3. preserve alphabetic order (avoid ["Ride", "Run"])

    Below code will still work when you introduce VirtualLift:

    let newSportsArray = Set( // 2. remove duplicates
    sportsArray.map {
        $0.replacingOccurrences(of: "Virtual", with: "") // 1. remove prefix
    })
    .sorted() // 3. prevent arbitrary order in Set and convert to Array
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