[brailleblaster] Re: MDI, SWT, etc.

  • From: "John J. Boyer" <john@xxxxxxxxxxxxxx>
  • To: brailleblaster@xxxxxxxxxxxxx
  • Date: Wed, 1 Dec 2010 13:03:53 -0600

Michael,

Well, I'm still getting used to object-oriented programming. Thanks for 
your patience and that of others on the list. What is a singleton 
pattern?

The snipet looks interesting. I will also check the link you give in 
another message for internationalization.

John
On Wed, Dec 01, 2010 at 02:57:06PM +0000, Michael Whapples wrote:
> I said I would get back with other comments.
> 
> You mention there should only be one Display object per application, 
> simple to ensure this by using a singleton pattern (there are better 
> ways of doing it than static initialisers).
> 
> The question comes though, should display belong to part of the word 
> processing part of BrailleBlaster? I think no as there may be other user 
> interface stuff at some point and what's going to contain the various 
> document windows/frames/composites? As an example of part of the user 
> interface outside the word processor part, I have a memory that the 
> specification said when BrailleBlaster starts a dialog will be shown 
> offering the user various options of what they can do.
> 
> May be what is needed is some utilities classes, things like the Display 
> object may be needed by user interface elements but it doesn't define 
> what they are.
> 
> On the note of defining what something is, you still seem to be missing 
> the point of interfaces, they aren't an alternative to abstract classes, 
> they complement them. Coming back to my person example, someone may be 
> many things (eg. female/male, computer programmer, software developer, 
> Braille reader, Braille writer, musician, sales person, etc) and they 
> can be many of these, but a person only has one way of doing the task 
> which may be common to many people but may not be defined by what they 
> are. As an example two people may multiply numbers in the same way, 
> regardless of if they are male or female, but someone else might 
> multiply numbers in another way despite being the same gender as one of 
> the two using the first system. This means we have common implementation 
> for multiplication but that commonality does not define gender or any 
> other role and that is when an abstract class is used. Abstract methods 
> exist so you can depend on a method which may not be common at that point.
> 
> Now just add in the single inheritance of Java with classes and I think 
> purely using abstract classes to define roles really will hold you back.
> 
> Now on a wider note, interfaces are possibly required for Java due to 
> its static typing, a dynamic language like python would not need 
> interfaces, but for some reason that dynamic idea hasn't really sat well 
> with me (if you can be handed any type then how can you guarantee what 
> you expect to find will be present).
> 
> Michael Whapples
> On 01/12/10 03:02, John J. Boyer wrote:
> >Where can I find a Java package for handling MDI? There is nothing
> >obvious in SWT.
> >
> >One reason I was thinking of having a WindowCommon class is that an
> >application should have only one instance of the Display widget. It
> >could go in a static initializer in WindowCommon.
> >
> >It seems to me that an abstract class combines the advantages of an
> >ordinary class and an interface. The methods defined in that clas can be
> >called from a class which extends it, and that class can also implement
> >methods which are only declared as in an interface.
> >
> >With MDI the class hierarchy becomes something like WPManager,
> >DocumentManager, Daisy and braille wondows.
> >
> >John
> >
> 

-- 
John J. Boyer, Executive Director
GodTouches Digital Ministry, Inc.
http://www.godtouches.org
Madison, Wisconsin, USA
Peace, Love, Service

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