Bakery Example

Bakery.swift

import Foundation

class Bakery {
    func bakeCake() -> Cake? {
        let ingredientStorage = IngredientStorage()
        if let chocolateFlavor = ingredientStorage.consume(flavor: .chocolate) {
            return Cake(flavor: chocolateFlavor)
        } else if let vanillaFlavor = ingredientStorage.consume(flavor: .vanilla) {
            return Cake(flavor: vanillaFlavor)
        }
        return nil
    }
}

struct Cake: CustomStringConvertible {
    let flavor: Flavor
    var description: String {
        return "\(flavor) cake"
    }
}

enum Flavor {
    case chocolate
    case vanilla
}

class IngredientStorage {
    private var pretendStorage: [Flavor] = [.vanilla, .chocolate]
    
    func consume(flavor: Flavor) -> Flavor? {
        guard let index = pretendStorage.index(of: flavor) else { return nil }
        pretendStorage.remove(at: index)
        return flavor
    }
}


let bakery = Bakery()
let cake = bakery.bakeCake()