Smalltalk and Object Orientation: an Introduction - Free

important, as these facilities handle everything from creating the window to handling user
interaction (e.g. input and output).
2. The other major change is that we have broken the Organizer class down into its constituent
parts. i.e. we now have separate classes for the address, appointments and notes functionality. the
Organizer class now acts as a composite class which obtains its functionality from the instances
it will possess.
The VisualOrganizer now works by displaying a Launcher window when the
VisualOrganizer is sent the message open. This message is like new except it not only creates a
new instance of a class, it also causes that instance to open whatever window is defined in the default
window definition method. This method is called windowSpec and is maintained on the class side. The
VisualOrganizer Launcher is illustrated in Figure 28.1.
28.2.1 Constructing the Launcher
First of all we need to define the class category we are going to put our classes in. The category will be
called 'Visual Organizer Classes’. If you wish to follow the example in this chapter yourself, you should
create this category now.
Next we will define the layout of the VisualOrganizer Launcher window. To do this we use the
VisualWorks User interface builder. As we are creating a completely new application you should launch
the user interface builder from the VisualWorks Launcher using the easel icon (if you are unclear on
what the user interface builder does see the last chapter).
Having launched the user interface builder, the first thing to do is to give the window as a whole a
label. This can be done using the properties option available from the right mouse button menu (or
middle if you have a three button mouse). Note that the properties window will display the properties of
the selected widget or the window as a whole if no widget is selected.
I have chosen to use the label “Visual Organizer” for my window, however you can use whatever
label you feel is most appropriate as the label is not significant for the operation of the system. Once
you have provided a suitable label select accept and close the properties window. Next resize the canvas
as appropriate. You are now ready to begin constructing the Visual Organizer Launcher.
The window layout for the Launcher is illustrated in Figure 28.2. It shows that four buttons have
been placed on the window. The text boxes with arrows indicate the action properties assigned to each
button.
Action: openDiary
Action: openNotes
Action: openAddresses
Action: doExit
Figure 28.2: Defining the actions for the Launcher's buttons
Each button is a basic action button with a textual label rather than an icon. Place each button on the
window using the palette as indicated in Figure 28.2. Remember you can use the button widget with the
multiple placement option (the box in the top right hand corner of the Palette) to place more than one
button. Then use the properties tool to ensure that the button properties match those in the diagram.
The Exit button also possesses a number of look preferences. These are set using the Color option in
the properties tool. The actual colors selected are:
• Foreground color: white and Background color: Royal Blue
• Selection Foreground Color: Pale Blue and Selection Background Color: Red
The first two colors are used to display the button on the window. The Foreground color relates to
the color in which the text on the button is displayed and the background color the is the main color of
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