The PackageInfo system is a simple, lightweight way of organizing Smalltalk source: it is nothing more than a naming convention, which uses (or abuses) the existing categorization mechanisms to group related code. Let me give you an example: say that you are developing a framework named SqueakLink to facilitate using relational databases from Squeak. You will probably have a series of system categories to contain all of your classes, for example,
('SqueakLink-Connections' OracleConnection MySQLConnection PostgresConnection) ('SqueakLink-Model' DBTable DBRow DBQuery)
and so on. But not all of your code will reside in these classes - you may also have, for example, a series of methods to convert objects into an SQL friendly format:
Object>>asSQL String>>asSQL Date>>asSQL
These methods belong in the same package as the classes in SqueakLink-Connections' and 'SqueakLink-Model'. You mark this by placing those methods in a method category (of Object, String, Date, and so on) named 'squeaklink' (note the initial star). The combination of the 'SqueakLink-...' system categories and the 'squeaklink' method categories forms a package named "SqueakLink".
The rules, to be precise, are this: a package named "Foo" contains
To get a feel for this, try loading the [Refactoring Browser] (http://map1.squeakfoundation.org/sm/package/b9a1179e-7c5f-4c97-8497-cf2ad468f6e6) into a Squeak image. The Refactoring Browser code uses PackageInfo's naming conventions, using "Refactory" as the package name. In a workspace, create a model of this package with
refactory := PackageInfo named: 'Refactory'.
It is now possible to introspect on this package; for example,
classes will return the long list of classes that make up the Refactoring
refactory coreMethods will return a list of MethodReferences for
all of the methods in those classes.
refactory extensionMethods is perhaps
one of the most interesting queries: it will return a list of all methods
contained in the Refactory package but not contained within a Refactory class.
This includes, for example,
Since the PackageInfo naming conventions are based on those used already by
Squeak, it is possible to use it to perform analysis even of code that has not
explicitly adapted to work with it. For example,
'Collections') externalSubclasses will return a list of all Collection
subclasses outside the Collections categories.
You can send
#fileOut to an instance of PackageInfo to get a changeset of
the entire package.