Avoid using Smalltalk at: to determine a class name or to reference a global variable. As well as being a potential source of packaging problems, this technique is generally bad practice. (It is frequently used to bypass prerequisite rules.)

The packager determines which class and global variables should be included in the packaged image by examining static references to classes and globals in your code. Because Smalltalk at: is dynamic, the packager might be unable to determine the correct references and therefore might omit certain classes and global variables from the packaged image.

Your packaged image will generate an error if it attempts to use an omitted class. The packaged image will contain a reference to nil in place of the class that has been excluded. Typically, the error will be UndefinedObject does not understand new. See Advanced packaging for details.