Protected and private visibility in Ruby - Mini Project: Build & Apply

Understanding Protected and Private Visibility in Ruby

📖 Scenario: Imagine you are creating a simple Ruby class to represent a bank account. You want to control access to certain methods to protect sensitive information and actions.

🎯 Goal: You will build a Ruby class BankAccount that uses protected and private methods to control access to balance information and withdrawal actions.

📋 What You'll Learn

Create a class called BankAccount with an instance variable @balance

Add a protected method called display_balance that returns the balance

Add a private method called withdraw that subtracts an amount from the balance

Add a public method called transfer that uses withdraw and display_balance to transfer money between accounts

Print the balance of both accounts after the transfer

💡 Why This Matters

🌍 Real World

Controlling access to sensitive data and actions is important in real-world applications like banking software to prevent unauthorized access or changes.

💼 Career

Understanding method visibility is essential for writing secure and maintainable Ruby code, a skill valued in software development jobs.

1

Create the BankAccount class with initial balance

Create a class called BankAccount with an initialize method that sets an instance variable @balance to the value passed as a parameter.

Ruby

# Define class BankAccount
# Add initialize method with parameter amount
# Set @balance to amount
class BankAccount
  def initialize(amount)
    # Your code here
  end
end

Need a hint?

Use def initialize(amount) and set @balance = amount.

2

Add a protected method to display balance

Inside the BankAccount class, add a protected method called display_balance that returns the value of @balance.

Ruby

class BankAccount
  def initialize(amount)
    @balance = amount
  end

  # Add protected method display_balance
  # Your code here
end

Need a hint?

Use the protected keyword before defining def display_balance.

3

Add a private method to withdraw money

Inside the BankAccount class, add a private method called withdraw that takes an amount parameter and subtracts it from @balance.

Ruby

class BankAccount
  def initialize(amount)
    @balance = amount
  end

  protected

  def display_balance
    @balance
  end

  # Add private method withdraw(amount)
  # Your code here
end

Need a hint?

Use the private keyword before defining def withdraw(amount).

4

Add a public transfer method and print balances

Add a public method called transfer that takes another BankAccount object and an amount. It should call withdraw(amount) on the current object and add the amount to the other account's @balance directly. Then, create two accounts, transfer 50 from the first to the second, and print both balances using display_balance.

Ruby

class BankAccount
  def initialize(amount)
    @balance = amount
  end

  protected

  def display_balance
    @balance
  end

  private

  def withdraw(amount)
    @balance -= amount
  end

  # Add public method transfer(other_account, amount)
  # Your code here
end

# Create two BankAccount objects
# Transfer 50 from first to second
# Print balances of both accounts
# Your code here

Need a hint?

Use withdraw(amount) to reduce balance, other_account.display_balance to get the other balance, and instance_variable_set to add to it. Use send(:display_balance) to print balances.