Smalltalk and Object Orientation: an Introduction - Free

the button. The selection colors are the colors which the button changes to when a user selects the exit
button. The contrast between red and blue helps the user identify that they have selected this button.
You have now defined all that is required to display the window. You are therefore ready to install
the window onto a class. To do this you should now select the Install button from the Canvas Tool
window. You should install the window on a class called VisualOrganizer which is a subclass of
ApplicationModel. The window selector name should be left as windowSpec. Don’t forget to
change the category to Visual Organizer Classes otherwise it will be placed in the default category.
Once you have installed the window onto a class you are now ready to define the action methods for
the window (a.k.a. the method t o run when the button is clicked). You can do this by selecting the
Define option in the Canvas Tool window. Do this now. The definer should define four methods named
after the action properties you defined above.
28.2.2 The VisualOrganizer class
Now go to the System Browser and look at the class definition for VisualOrganizer. You will see that a
full class definition has been generated for you by the User interface builder. Your newly created class
definition should look like this:
ApplicationModel subclass: #VisualOrganizer
instanceVariableNames: ''
classVariableNames: ''
poolDictionaries: ''
category: 'Visual Organizer Classes'
Next add a class comment. This is left as an exercise for the reader.
28.2.3 The “actions” protocol
Methods for each of the buttons in t he window are defined by the User interface builder when the
Define option is selected (the user can select not to define methods using a scrolling selection window).
These methods are placed in the “actions” protocols. By default, these methods are define d to return the
value of self. For example, the definitions generated by the User interface builder are:
openAddresses
^self
openNotes
^self
openDiary
^self
doExit
^self
If we wish them to do anything useful, then we need to edit these methods and define what they should
do.
We shall first look at the doExit method as this is the simplest method. This method will close the
window. To do this we use the closeRequest method defined in the ApplicationModel class.
We therefore merely need to send the message closeRequest to self.
doExit
"This method closes the associated window"
self closeRequest.
This method is associated with the “exit” button on the VisualOrganizer Launcher.
The other three actions are associated with the three launch buttons on the VisualOrganizer
Launcher. These are used to open the address book, the diary and the notes tool. The openDiary and
openNotes methods will remain unchanged. They will return self when called. Extending the
application for appointments and notes is left as an exercise for the reader.
The only action method which possesses “content” will be openAddress book. This should send
the message open to the AddressBook class. This causes an instance of AddressBook to be
created and the default window defined on this class opened:
openAddresses
AddressBook open.
Define this now and accept it (leave any classes undefined when VisualWorks warns you about them).
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