Smalltalk and Object Orientation: an Introduction - Free

28.3 The AddressBook class
28.3.1 The AddressBook window
Input Field
Aspect: name
Text Label
Text Label
Text Editor
Aspect: address
Action Button
Action: doInput
Action Button
Action: doQuery
Action Button
Action: doExit
Figure 28.3: The layout and definition of the AddressBook window
Figure 28.3 illustrates the layout of the AddressBook window. As can be seen it has two input fields as
well as three buttons and two text labels. The specifications for these different widgets are indicated in
the figure. Using the palette and the properties tools define the window following the steps outlined
above.
For the window as a whole I have used the label “Add ress Book” however as before you can use
whatever label you feel appropriate. The three buttons along the bottom of the window will be referred
to these as input, query and exit (from left to right).
Once you have defined the layout of the window and the v arious properties you are ready to install
the window on a class. To do this select the Install button from the Canvas Tool window and install the
window on a class called AddressBook which is a subclass of ApplicationModel. 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 can select the Define option in the Canvas Tool
window to define the instance variables and accessor methods for the two aspects (input fields) and the
actions for the buttons (a.k.a. the method to run when the button is clicked). You are now ready to
define the functionality of the AddressBook class.
28.3.2 The AddressBook class definition
In the System Browser, have a look a t the class definition for AddressBook. You will see that a full
class definition has been generated for you by the User interface builder. You now need to add the
instance variable specific to the functioning of the class (rather than the instance variabl es specific to
the user interface). This variable will be called addressBook. Once you have done that, your newly
created class definition should look like:
ApplicationModel subclass: #AddressBook
instanceVariableNames: 'name address addressBook '
classVariableNames: ''
poolDictionaries: ''
category: 'Visual Organizer Classes'
Don’t forget to accept the class definition. The class comment is left as an exercise for the reader (you
must get use to defining them). You should also note that when you sele cted the AddressBook class
there were two method protocols defined for you already. These were ‘aspects’ and ‘actions’. The
‘aspects’ hold the instance variable access methods and the ‘actions’ hold the methods which will be run
when the buttons are clicked.
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