specifying access control

ch03/specifying_access_control/08.rb

@@ -0,0 +1,37 @@
+class Account
+  attr_accessor :balance
+  def initialize(balance)
+    @balance = balance
+  end
+end
+
+class Transaction
+  def initialize(account_a, account_b)
+    @account_a = account_a
+    @account_b = account_b
+  end
+  private
+    def debit(account, amount)
+      account.balance -= amount
+    end
+    def credit(account, amount)
+      account.balance += amount
+    end
+  public
+    def transfer(amount)
+      debit(@account_a, amount)
+      credit(@account_b, amount)
+    end
+end
+
+savings = Account.new(100)
+checking = Account.new(200)
+
+puts "Savings balance is #{savings.balance}"
+puts "Checking balanace is #{checking.balance}"
+
+trans = Transaction.new(checking, savings)
+trans.transfer(50)
+
+puts "Savings balance is #{savings.balance}"
+puts "Checking balanace is #{checking.balance}"