Withdraw Method

Part of the Object Oriented Programming section of Coddy's Lua journey — lesson 21 of 70.

Challenge

Easy

Your Digital Bank is growing! Accounts can now receive deposits, but a real bank also needs to let customers take money out. Let's add a :withdraw(amount) method—but with an important safety check.

Unlike deposits, withdrawals can fail. If a customer tries to withdraw more money than they have, the bank shouldn't allow it. Your withdraw method needs to check if sufficient funds exist before deducting the amount.

You'll continue working with your two files:

Account.lua: Add a :withdraw(amount) method to your existing Account class. If the account has enough balance, subtract the amount and return true. If there aren't sufficient funds, print Insufficient funds and return false without changing the balance.
main.lua: Create an account, make a deposit to give it some funds, then attempt several withdrawals to see both successful and failed transactions.

You will receive four inputs:

Initial deposit amount
First withdrawal amount
Second withdrawal amount
Third withdrawal amount

In your main file, create an account, deposit the initial amount, then attempt each withdrawal in order. After each withdrawal attempt, print the current balance on a new line. Remember that failed withdrawals will also print Insufficient funds before you print the balance.

For example, if the inputs are 100, 30, 50, and 40, the output should be:

70
20
Insufficient funds
20

The account starts with 100 after the deposit. The first withdrawal of 30 succeeds (balance: 70), the second withdrawal of 50 succeeds (balance: 20), but the third withdrawal of 40 fails because only 20 remains—so the balance stays at 20.

Try it yourself

-- Require the Account module
local Account = require('Account')

-- Read the four inputs
local initialDeposit = tonumber(io.read())
local withdrawal1 = tonumber(io.read())
local withdrawal2 = tonumber(io.read())
local withdrawal3 = tonumber(io.read())

-- Create a single account
local account = Account:new()

-- Deposit the initial amount
account:deposit(initialDeposit)

-- Attempt first withdrawal and print balance
-- TODO: call account:withdraw(withdrawal1) here
print(account.balance)

-- Attempt second withdrawal and print balance
-- TODO: call account:withdraw(withdrawal2) here
print(account.balance)

-- Attempt third withdrawal and print balance
-- TODO: call account:withdraw(withdrawal3) here
print(account.balance)