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So far, you have seen that a changed: message causes update:
messages to be sent. Now, you need to know that such changed messages are
most often sent inside setters, as in the following setters of the x
and y instance variables. Note that the aspect argument identifies
the instance variable—that is, the aspect—that changes.
ModelSubclass method definition • instance setX: value x := value. self changed: #x. ModelSubclass method definition • instance setY: value y := value. self changed: #y. Workspace M setX: 0. M setY: 1. Transcript Sample viewer receiving #x update message Sample viewer receiving #y update message