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Ruby Ruby Foundations Methods Class Methods

Posted by M Fen
M Fen
9,858 Points

Why do I get "=> nil" after creating an attr_reader : transactions method, reloading the file, making deposits etc?

created the attr_reader : transactions on the top of my file per the video but why does it return "nil" after I save the file, reload in irb, making some deposits and withdraws and then call on bank_account.transactions in IRB?

Is it because it was never defined in the initialize method? 

class BankAccount

#Attribution
    attr_reader :balance
    attr_reader :transactions

# Class Methods
    class << self
        def create_for(first_name, last_name)
            @accounts ||= []
            @accounts << BankAccount.new(first_name, last_name)
        end

        def find_for(first_name, last_name)
            @accounts.find{|account| account.full_name =="#{first_name} #{last_name}"}
        end

    end

#Instance Methods
          def initialize(first_name, last_name)
             @balance = 0
             @first_name = first_name
             @last_name = last_name
          end

          def full_name
            "#{@first_name} #{@last_name}"
          end

          def deposit(amount)
            @balance += amount
          end

          def withdraw(amount)
            @balance -= amount
          end

end

2 Answers

Maciej Czuchnowski
Maciej Czuchnowski
36,441 Points
Maciej Czuchnowski
Maciej Czuchnowski
36,441 Points

I don't see any line which would instantiate or modify the @transactions variable in any way, so you can't expect it to contain anything. Basically you have a method for reading the contents of @transactions variable that is always empty (nil) because you never did anything to any variable called @transactions at any point in the code.

Look at @balance: it starts off as 0 in the initialize, so whenever you create a new account, you can read its balance and you will get at least 0, and then you have two methods that modify that variable (deposit and withdraw, and they do something to that variable).

Maciej Czuchnowski
Maciej Czuchnowski
36,441 Points
Maciej Czuchnowski
Maciej Czuchnowski
36,441 Points

In order to have this working in the most basic version (counting the number of transactions made in the account), you would have to add this to your initialize method:

@transactions = 0

and this to both your deposit and withdraw methods:

@transactions += 1

This will add 1 to transactions of that account anytime you deposit or withdraw money from it.

M Fen
M Fen
9,858 Points
M Fen
M Fen
9,858 Points

That makes sense. I figured it was because it was never added to the init method.

Thanks a mill for the working example too.