Part 3:Keeping Our Balance What is the role/function of this method?

I can't seem to get to the video to see exactly what he's describing here, but yeah it's effectively re-writing the .to_s method for the given object (I think bank account in this case?) so that you can use .to_s (or 'puts' which just calls .to_s - literally 'put to string') to print out what you specify in this new method definition.

eg.

@bank_account = BankAccount.new('Jason')

if the @bank_account has an attr_reader for name then you can call it with @bank_account.name --> should return 'Jason'

Likewise with the account balance, if you have defined a method to return the balance (as I think Jason has done in the video):

@bank_account.balance --> will return the balance (something like 10.00)

So if you specify that the account prints out its name and dollar/cents balance as part of the to_s method, you don't have to manually type all that out each time yourself. You just specify in the new to_s definition what properties of the @bank_account you want it to print out, and that's what it will print when you call to_s.

# So if @bank_account.name == "Jason"
# and @bank_account.balance == 10.00

def to_s 
    "Name: #{name}, Balance of account : #{sprintf("%0.2f", balance)}"
end

puts @bank_account # --> will print out "Name: Jason, Balance of account : 10.00"
@bank_account.to_s # --> will also print this out.

That was a bit wordier that I intended, hope it makes more sense what he's doing now.