Vending machine vend() function refactored

VendRefactored.swift

func vend(itemNamed name: String) throws {
    let item = try validatedItemNamed(name)
    reduceDepositedCoinsBy(item.price)
    removeFromInventory(item, name: name)
    dispense(name)
}

private func validatedItemNamed(name: String) throws -> Item {
    let item = try itemNamed(name)
    try validate(item)
    return item
}

private func reduceDepositedCoinsBy(price: Int) {
    coinsDeposited -= price
}

private func removeFromInventory(var item: Item, name: String) {
    --item.count
    inventory[name] = item
}

private func itemNamed(name: String) throws -> Item {
    if let item = inventory[name] {
        return item
    } else {
        throw VendingMachineError.InvalidSelection
    }
}

private func validate(item: Item) throws {
    try validateCount(item.count)
    try validatePrice(item.price)
}

private func validateCount(count: Int) throws {
    if count == 0 {
        throw VendingMachineError.OutOfStock
    }
}

private func validatePrice(price: Int) throws {
    if coinsDeposited < price {
        throw VendingMachineError.InsufficientFunds(coinsNeeded: price - coinsDeposited)
    }
}