From: Tom Sawyer <transami@...>
Date: 2002-07-21T04:19:39+09:00
Subject: Re: GUI's and the Rouge, Part II

On Sat, 2002-07-20 at 12:25, Ned Konz wrote:
> The main problem with this is that the data shouldn't have to know 
> about how it's going to be presented.
> 
> When you want to display something on (say) a PDA, you might choose to 
> have different representations (shorter strings, no colors, etc.).
> 
> Maybe the best strategy would be to have an intervening policy object 
> between the data and the widgets that determines how a given piece of 
> data would be presented in a particular kind of UI.

thanks Ned,
a good point. but thanks to ruby we can deal with this farily easily w/o
having to resort to intervening objects by seperating parts of a class
definition. just as one extends a class now one can create conditional
extenstions dependent, say, on the platform. for exmaple:

pda.rb:
class MyClass
  def initialize  
    super
    avar.extend RougeDeux::WidgetFactory(:Label)
    avar.style={:width=>10}
  end
end

pc.rb:
class MyClass
  def initialize  
    super
    avar.extend RougeDeux::WidgetFactory(:Label)
    avar.style={:width=>100}
  end
end

myapp.rb:
class MyClass
  attr_accessor avar
  def initialize
    @avar = "" 
  end
end
require pda.rb if $interface='PDA'
require pc.rb if $interface='PC'

so this is one approach. in a sense it is like an intervening object,
only it's an intervening definition. (note: this does "confuscate" the
object, but it does it in a clean, well seperated manner) i'm sure there
are others ways. one thing i hadn't taken into account, that your post
made me consider is the idea of stylesheets --convenient ways to set the
properties of a large number of widgets at once. but i'm sure that would
not be too difficult to factor in.

~transami





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~transami

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