Add another observer : Observer « Design Patterns « Ruby

1. Ruby
2. Design Patterns
3. Observer

Add another observer

class PaymentObserver
  def update( changed_employee )
    puts("Cut a new check for #{changed_employee.name}!")
    puts("His salary is now #{changed_employee.salary}!")
  end
end

class Employee
  attr_reader :name, :title
  attr_reader :salary

  def initialize( name, title, salary )
    @name = name
    @title = title
    @salary = salary
    @observers = []
  end

    def salary=(new_salary)
      @salary = new_salary
      notify_observers
    end
    def notify_observers
      @observers.each do |observer|
        observer.update(self)
      end
    end
    
    def add_observer(observer)
      @observers << observer
    end
    
    def delete_observer(observer)
      @observers.delete(observer)
    end
    
end

fred = Employee.new('Fred', 'Crane Operator', 30000.0)

payroll = PaymentObserver.new
fred.add_observer( payroll )

fred.salary=35000.0

class TaxMan
  def update( changed_employee )
    puts("Send #{changed_employee.name} a new tax bill!")
  end
end

tax_man = TaxMan.new
fred.add_observer(tax_man)
fred.salary=90000.0

 

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