Setting application prerequisites
When you set prerequisites, you need to consider:
What application contains the class that you want to subclass from? Though the class you want to subclass from is loaded in your image, your application (or, as the case may be, its subapplication) must have the application containing that class in its prerequisite chain in order to see it.
What application does your application (and its subapplications) need to run? For example, suppose you have the applications AbcApplication and XyzApplication. XyzApplication provides the platform connections that AbcApplication needs to run. Therefore, XyzApplication must be named a prerequisite of AbcApplication.
When you created DevelopChooser, you selected Kernel as the prerequisite. As Kernel is one of the base applications in Smalltalk, naming it the prerequisite enables you to subclass from about 100 classes.
To find out what classes are visible to your application when Kernel is the prerequisite, do the following:
1. From an Application Manager with DevelopChooser highlighted in the list of applications, select Browse Application from the Applications menu. This opens an Application Browser on your application.
2. From the Classes menu, select Visibility > Add Prerequisite Classes. The names of all classes contained in Kernel, its subapplications, and your application are shown in the list of classes. With Kernel as the prerequisite, your application can subclass from any one of these classes.
When you define classes for DevelopChooser, you will subclass from Object, which is visible (or contained in the list of classes displayed).
Last modified date: 01/29/2015