This chapter is from the book
This chapter is from the book
This chapter is from the book
This chapter is from the book
Inviting Message
Sometimes as you are writing code, you expect that people will want to vary a part of the computation in a subclass. Send an appropriately named message to communicate the possibility of later refinement. The message invites programmers to refine the computation for their own purposes later.
If there is a default implementation of the logic, make it the implementation of the message. If not, declare the method abstract to make the invitation explicit.