Smalltalk and Object Orientation: an Introduction - Free

Figure 15.4: Creating a project
To enter the project select the enter button on the window. To exit a project select the Exit project
option from the VisualLauncher from within the project. Exiting the project in this way will bring you
back up a level and your desktop will be restored to the state it was in when you entered the project.
You can delete a project by closing the project window. For example, if I wished to destroy the project
in Figure 15.4, then I would close that window using the Windows-95 close icon.
Root
User Interface
Data
Management
Operations
Database
interface
Sensor
interface
Figure 15.5: Project hierarchy
Projects can be nested hierarchically to any depth (although it is rarely useful to go beyond 2 or 3
levels). This means that the project structure illustrated in Figure 15.5 can easily be constructed. In this
structure, at the top level the developer sees the User Interface project, the Data Management project
and the Operations project. When the user enters the Data Management project, then they see the
Database Interface project and the Sensor Interface project.
This means that, when they are working on the user interface project, they do not see the windows
they have been us ing in any of the other projects. They can thus leave one of the other projects in a
particular state and come back to it later.
15.5.3 Changes and projects
In addition to the changes file created for the whole imag e, a project has its own changes set. This
changes set is a summary of the changes which have been made to that project. This means that, unlike
the changes file, it does not include all changes to the system. Instead it lists those classes which have
been modified within the current project.
The changes set of a project can be accessed using the Inspect ChangeSet option from the changes
menu on the VisualLauncher. If you wish to save the changes made to a project, you can do it using the
file out as .. option from the right mouse button menu (middle on a three button mouse) available from
the left hand window of this inspector. This can be a useful way of exchanging changes with other
developers.
15.5.4 Warnings about projects
There are two points you should note about projects. The first it that they are only a visual aid to project
organization. That is, all the source code changes you make are global to the current image. Many
developers when they first encounter projects assume that changes in one project will be limited to that
project. They aren’t and this can be rather counter intuitive. Care should therefore be taken when
modifying classes in one project which may be used in another project. Secondly, as all changes are
actually made to the whole image, it i s a mistake to assume that when a project is deleted, its affects
will also be deleted.
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