code.swift

enum VendingMachineError: Error {
    case invalidSelection
    case insufficientFunds(coinsNeeded: Int)
    case outOfStock
}

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


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


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


        coinsDeposited -= item.price


        var newItem = item
        newItem.count -= 1
        inventory[name] = newItem


        print("Dispensing \(name)")
    }
}