BankAccount

class BankAccount {
    private let accountNumber: String
    private var balance: Double

    init(balance: Double) {
        self.accountNumber = UUID().uuidString
        self.balance = balance
    }

    var balanceChanged : ((Double) -> Void)?
    func deposit(amount: Double) {
        balance += amount
        notifyBalanceChange()

    }
    func amountWithdraw(amount: Double) {
        if amount <= balance {
            balance -= amount
            notifyBalanceChange()

        }
        else {
            print("There is not enough money !!")
        }
    }
    private func notifyBalanceChange() {
        if let balanceChanged = balanceChanged {
                 balanceChanged(balance)
            print("Balance has changed !!")
             }
    }
}


let bankAccount = BankAccount(balance: 1000)
bankAccount.balanceChanged = { newBalance in
    print("Balance changed...New balance: \(newBalance)")
}
bankAccount.deposit(amount: 500)
bankAccount.amountWithdraw(amount: 200)