Transfering data between objects

From: Cobus Kruger (spamwontwork_at_kplanet.co.za)
Date: 12/08/04

  • Next message: Alan Gauld: "Re: Booch and UML" 
    Date: 7 Dec 2004 23:22:29 -0800

    Hi Guys,

    I am again struggling with a recurring problem that I am sure there
    must be a pattern for.

    I have a two hierarchies of classes. One of them is a hierarchy of
    business objects and the other is a hierarchy of screens to
    display/modify those objects. In both cases, an abstract base class
    allows me to polymorphically call things like load, post and validate.
    Screens know bits and pieces of the business objects they represent,
    but mostly the screens and business objects are associated dynamically.

    This worked well. Until I received requirements for new validations on
    the screens. Some of these new validations require that the screen know
    a little about an object not already associated with it. That bit makes
    me a little uncomfortable, but it isn't real problematic.
    Unfortunately, the object that is now needed is bound to another
    screen, and the attributes required may not have been posted to the
    object yet - that only happens behind an OK button. This implies that
    my one screen needs to be coupled to another screen. Ouch.

    In other instances that I have had problems passing data between
    objects that must remain uncoupled, I have defined a data packet that
    can be published. Each object can then access the datapacket (various
    levels of control may be in place but is irrelevant to the basic
    concept). This also works well enough, but sometimes mean that the
    packet becomes like a really large global store that constantly needs
    to have certain fields synchronized.

    There must be a better way, I'm sure. How do I pass data between two
    objects that are and should remain decoupled?

    Regards,

    Cobus

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