The 'Gang of Four' Companion:

Observer Design Pattern

Formal specification of design patterns in LePUS3 and Class-Z

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This page is part of the The 'Gang of Four' Companion dedicated to the formal specification in LePUS3 and Class-Z of patterns from the 'Gang of Four' catalogue [Gamma et al 1995].

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The Observer design motif

The informal description: Excerpts from [Gamma et al. 1995] (adapted for this purpose):

Intent: Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.

Structure: Original OMT diagram converted to UML (Why and How?):

Observer in UML

Participants:

Collaborations:

Formal specification

See also:

Observer in LePUS3
Observer in LePUS3 (legend)
Observer in Class-Z (legend)