From: stefano <scobianchi@...>
Date: 2003-05-12T22:22:13+09:00
Subject: Re: [OO interface design] Pass-by reference VS encapsulation ?

On Wed, 30 Apr 2003 21:17:23 +0000, Simon Vandemoortele wrote:

>>   a) contacts can be aware that they are 'contained' (in an address book)
>>   b) contact methods use this awareness when ri can be violated
> Yes, that is what I meant by a solution where 'the contacts cooperate
> with the addressbook'.
> I don't know ... but I do feel the potential for re-using the Contact
> class outside the Addressbook is rather limited anyway so I wouldn't
> feel too bad about coupling them.


Well, you could have a base class "Contact" and a derived class
"BoundContact" (sorry, can't think of a better name :-)

silly example:

--CUT--
class Contact
  def initialize(someValues)
    @name = someValues['name']
    ...
  end

  def setName(aName)
    @name = aName
  end

  def to_h
    {
      'name' => @name
      ...
    }
  end

  def putInAddressBook(aBook)
    return BoundContact.new(aBook, to_h)
  end
end

class BoundContact < Contact
  def initialize(anAddressBook, someValues)
    @addressBook = anAddressBook
    super
  end

  def setName(aName)
    unless @addressBook.findContact(aName)
      super
    else
      raise "Contact '#{aName}' already exists"
    end
  end

  def getUnboundContact
    return Contact.new(to_h)
  end
end
--CUT--

silly example, using encapsulation:

--CUT--
class Contact
  def initialize(someValues)
    @name = someValues['name']
    ...
  end

  def setName(aName)
    @name = aName
  end

  def to_h
    {
      'name' => @name
      ...
    }
  end

  def putInAddressBook(aBook)
    return BoundContact.new(aBook, self)
  end
end

class BoundContact
  def initialize(anAddressBook, aContact)
    @addressBook = anAddressBook
    @contact = aContact
  end

  def setName(aName)
    unless @addressBook.findContact(aName)
       @contact.setName(aName)
    else
      raise "Contact '#{aName}' already exists"
    end
  end

  def getUnboundContact
    return @contact
  end
end
--CUT--


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