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Ruby Ruby Objects and Classes Build a Bank Account Class Part 3: Keeping Our Balance

Erik Nuber
Erik Nuber
20,629 Points
Posted by Erik Nuber
Erik Nuber
20,629 Points

Using a hash symbol in the Balance Method

 def addTransaction(description, amount)
    @transactions.push(description: description, amount: amount)
  end

  def balance
    balance = 0.0
    @transactions.each do |transaction|
      balance += transaction[:amount]  
    end
    return balance
  end

I am trying to figure out how transaction[:amount] accesses the amount in the array. I would have thought it would be transaction[amount]. I have been back thru the hash course and was unable to find anything other than a few seconds referring to :arg1 being a symbol and that there could be only one versus just arg1. But nothing else mentioned referencing hashes with the hash[:arg1] format.

below is the full code but, don't think it is necessary so I separated out the areas in question above.

class BankAccount

  attr_reader :name

  def initialize(name)
    @name = name
    @transactions = []
    addTransaction("Beginning Balance", 0)
  end

  def credit(description, amount)
    addTransaction(description, amount)
  end

  def debit(description, amount)
    addTransaction(description, -amount)
  end

  def addTransaction(description, amount)
    @transactions.push(description: description, amount: amount)
  end

  def balance
    balance = 0.0
    @transactions.each do |transaction|
      balance += transaction[:amount]  
    end
    return balance
  end

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


  def printRegister
    puts "#{name}'s Bank Account"
    puts "-" * 40

    puts "Description".ljust(30) + "Amount".rjust(10)
    @transactions.each do |trans|
      puts trans[:description].ljust(30) + sprintf("%0.2f", trans[:amount]).rjust(10)
    end

    puts "-" * 40
    puts "Balance:".ljust(30) + sprintf("%0.2f", balance).rjust(10)
    puts "-" * 40
  end


end


bank_account = BankAccount.new("Whomever")
bank_account.credit("Paycheck", 100)
bank_account.debit("Groceries", 40)
puts bank_account.printRegister

1 Answer

PoJung Chen
PoJung Chen
5,856 Points
PoJung Chen
PoJung Chen
5,856 Points

This is because we push hash key with symbol by

@transactions.push(description: description, amount: amount)

This is same as 

@transactions.push({:description => description, :amount => amount})

Therefore, we can assess the value through @transaction[":description"]