如何返回 swift 中 function 的顶部？

Question

I have this function that picks a random value from a list:

func pickAttraction(attractionType: Array<Attraction>) -> Attraction {
  var randAttr = attractionType.randomElement()
  if favoritesNames.contains(randAttr!.attractionName) {
    return pickAttraction(attractionType: attractionType)
  } else {
    return randAttr!
  }
}

If the random value is in the array favoritesName, I want it to go back to the top of the function and pick a new value.

How can I make this more efficient?

In addition, is it possible for the program to crash while force-unwrapping randAttr (on line 3) if attractionType always has at least 8 values?

Answer 1

The question is not worth asking. It'll never get you there.

func pickAttraction(from attractions: [Attraction]) -> Attraction? {
  attractions.filter { !favoritesNames.contains($0.name) }
    .randomElement()
}

Answer 2

Here is a sample in playground

import UIKit
class RandomAttraction:Hashable{
    static func == (lhs: RandomAttraction, rhs: RandomAttraction) -> Bool {
        return lhs.attractionName == rhs.attractionName
    }
    func hash(into hasher: inout Hasher) {
        hasher.combine(attractionName)
    }

    init(attractionName:String) {
        self.attractionName = attractionName
    }
    var attractionName:String

}

var favoritesNames = [RandomAttraction.init(attractionName: "a"),RandomAttraction.init(attractionName: "b")]

var otherNames = [RandomAttraction.init(attractionName: "c"),RandomAttraction.init(attractionName: "d")]



func pickAttraction(attractionType: Array<RandomAttraction>) -> RandomAttraction? {
    //Filters the content of the favoritesNames from attractionType
   let filteredArray = Array(Set(attractionType).subtracting(favoritesNames))
    //If count is zero return nil
    if filteredArray.count == 0{
        return nil
    }
    let randAttr = filteredArray.randomElement()
    return randAttr
}

//MARK: Usage
if let pickedAttraction = pickAttraction(attractionType: otherNames){
    print(pickedAttraction.attractionName)
}else{
    print("No attractions")
}