From: Friedrich Dominicus <frido@...>
Date: 2002-09-17T15:52:55+09:00
Subject: Re: MVC and OO Design?

jcb@iteris.com (MetalOne) writes:

> Thanks to all for your help.
> 
> I was really thinking very abstractly about a problem in my head that
> MVC kind of demonstrated.  I was in search of deep answers in regards
> to when to include a function in a class and when not too.

Ok now after a an abstract example an fully fledged Ruby MVC
application. I've used ruby-gnome and

This is the application code
require 'lglade'

class Controller
  def initialize
    @glade = GladeXML.new("mvc_ruby.glade"){|handler| method(handler)}
    @tf_1 = @glade.widget("tf_number_one")
    @tf_2 = @glade.widget("tf_number_two")
    @sum_field = @glade.widget("tf_sum");
    @model = Model.new
  end

  def on_pb_calculate_clicked(widget, data)
    @sum = @model.add(@tf_1.get_text.to_f, @tf_2.get_text.to_f)
    @sum_field.set_text(@sum.to_s)
  end
  
  def quit
    Gtk.main_quit
  end
    
end
   


class Model
  def add (a, b)
    return a + b
  end
end

Controller.new
Gtk.main


The view is not seen as a extra class text here it's hidden behind the
@glade instance variable that's my View!

The .glade stuff is this (very fast thrown together, so please be
aware:
But please be aware too where the connection occures.
- the names for the textfields
- and the callback functon (enclosed in <handler>...</handler>)

This is what I would see as "exported" from the View.

I do not claims this to be excelleent ruby programming but I hope it
shows that MVC and OO do not fight each other. What could be improved
the
@tf_1.somethi.to_f chain is not nice one, one could hide it behin
another function. But you are invited to do it better than me ;-)

<?xml version="1.0"?>
<GTK-Interface>

<project>
  <name>MVC_ruby</name>
  <program_name>mvc_ruby</program_name>
  <directory></directory>
  <source_directory>src</source_directory>
  <pixmaps_directory>pixmaps</pixmaps_directory>
  <language>C</language>
  <gnome_support>True</gnome_support>
  <gettext_support>True</gettext_support>
</project>

<widget>
  <class>GtkWindow</class>
  <name>main_window</name>
  <title>MVC Example in Ruby</title>
  <type>GTK_WINDOW_TOPLEVEL</type>
  <position>GTK_WIN_POS_NONE</position>
  <modal>False</modal>
  <allow_shrink>False</allow_shrink>
  <allow_grow>True</allow_grow>
  <auto_shrink>False</auto_shrink>

  <widget>
    <class>GtkVBox</class>
    <name>vbox1</name>
    <homogeneous>False</homogeneous>
    <spacing>0</spacing>

    <widget>
      <class>GtkHBox</class>
      <name>hbox4</name>
      <homogeneous>False</homogeneous>
      <spacing>0</spacing>
      <child>
	<padding>0</padding>
	<expand>True</expand>
	<fill>True</fill>
      </child>

      <widget>
	<class>GtkLabel</class>
	<name>label4</name>
	<label>Zahl 1</label>
	<justify>GTK_JUSTIFY_CENTER</justify>
	<wrap>False</wrap>
	<xalign>0.5</xalign>
	<yalign>0.5</yalign>
	<xpad>0</xpad>
	<ypad>0</ypad>
	<child>
	  <padding>0</padding>
	  <expand>False</expand>
	  <fill>False</fill>
	</child>
      </widget>

      <widget>
	<class>GtkEntry</class>
	<name>tf_number_one</name>
	<can_focus>True</can_focus>
	<editable>True</editable>
	<text_visible>True</text_visible>
	<text_max_length>0</text_max_length>
	<text></text>
	<child>
	  <padding>4</padding>
	  <expand>False</expand>
	  <fill>False</fill>
	  <pack>GTK_PACK_END</pack>
	</child>
      </widget>
    </widget>

    <widget>
      <class>GtkHBox</class>
      <name>hbox5</name>
      <homogeneous>False</homogeneous>
      <spacing>0</spacing>
      <child>
	<padding>0</padding>
	<expand>True</expand>
	<fill>True</fill>
      </child>

      <widget>
	<class>GtkLabel</class>
	<name>label5</name>
	<label>Zahl 2</label>
	<justify>GTK_JUSTIFY_LEFT</justify>
	<wrap>False</wrap>
	<xalign>0.5</xalign>
	<yalign>0.5</yalign>
	<xpad>0</xpad>
	<ypad>0</ypad>
	<child>
	  <padding>4</padding>
	  <expand>False</expand>
	  <fill>False</fill>
	</child>
      </widget>

      <widget>
	<class>GtkEntry</class>
	<name>tf_number_two</name>
	<can_focus>True</can_focus>
	<editable>True</editable>
	<text_visible>True</text_visible>
	<text_max_length>0</text_max_length>
	<text></text>
	<child>
	  <padding>4</padding>
	  <expand>False</expand>
	  <fill>False</fill>
	  <pack>GTK_PACK_END</pack>
	</child>
      </widget>
    </widget>

    <widget>
      <class>GtkHBox</class>
      <name>hbox6</name>
      <homogeneous>False</homogeneous>
      <spacing>0</spacing>
      <child>
	<padding>0</padding>
	<expand>True</expand>
	<fill>True</fill>
      </child>

      <widget>
	<class>GtkLabel</class>
	<name>label6</name>
	<label>Sum</label>
	<justify>GTK_JUSTIFY_CENTER</justify>
	<wrap>False</wrap>
	<xalign>0.5</xalign>
	<yalign>0.5</yalign>
	<xpad>0</xpad>
	<ypad>0</ypad>
	<child>
	  <padding>4</padding>
	  <expand>False</expand>
	  <fill>False</fill>
	</child>
      </widget>

      <widget>
	<class>GtkEntry</class>
	<name>tf_sum</name>
	<can_focus>True</can_focus>
	<editable>True</editable>
	<text_visible>True</text_visible>
	<text_max_length>0</text_max_length>
	<text></text>
	<child>
	  <padding>4</padding>
	  <expand>False</expand>
	  <fill>True</fill>
	  <pack>GTK_PACK_END</pack>
	</child>
      </widget>
    </widget>

    <widget>
      <class>GtkButton</class>
      <name>pb_calculate</name>
      <can_focus>True</can_focus>
      <signal>
	<name>clicked</name>
	<handler>on_pb_calculate_clicked</handler>
	<last_modification_time>Tue, 17 Sep 2002 06:16:34 GMT</last_modification_time>
      </signal>
      <label>Calculate Sum</label>
      <relief>GTK_RELIEF_NORMAL</relief>
      <child>
	<padding>5</padding>
	<expand>False</expand>
	<fill>False</fill>
      </child>
    </widget>
  </widget>
</widget>
</GTK-Interface>

Very verbose this XML isn't it ;-(

Regards
Friedrich