// This is a sample code snipet from The Swift Programmin Language(Swift2.1)

enum VendingMachineError: ErrorType {
  case InvalidSelection
  case InsufficientFunds(coinsNeeded: Int)
  case OutOfStock
}

// Throwing error
throw VendingMachineError.InsufficientFunds(coinsNeeded: 5)

struct Item {
  var price: Int
  var count: Int
}

class VendingMachine
{
  var inventory = [
    "Candy Bar": Item(price: 12, count: 7)
    "Chips": Item(price: 10, count: 4)
    "Pretzels": Item(price: 7, count: 11)
  ]

  var coinsDeposited = 0

  func dispenseSnack(snack: String) {
    print("Dispensing \(snack)")
  }

  func vend(itemNamed name: String) throws {
    guard var item = inventory[name] else {
      throw VendingMachineError.InvalidSelection
    }

    guard item.count > 0 else {
      throw VendingMachineError.OutOfStack
    }

    guard item.price <= coinsDeposited else {
      throw VendingMachineError.InsufficientFunds(coinsNeeds: item.price - coinsDeposited)
    }

    coinsDeposited -= item.price
    --item.count
    inventory[name] = item
    dispenceSnack(name)
  }
}