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gptkbp:instanceOf
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Software design pattern
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gptkbp:advantage
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Can lead to memory leaks if observers are not properly removed
Can be inefficient with many observers
Notification order is not guaranteed
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gptkbp:alternativeName
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Publish-subscribe pattern
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gptkbp:author
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gptkb:Erich_Gamma
gptkb:John_Vlissides
gptkb:Richard_Helm
gptkb:Ralph_Johnson
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gptkbp:benefit
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Promotes loose coupling
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gptkbp:category
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Behavioral pattern
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gptkbp:commonIn
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Event-driven systems
GUI toolkits
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gptkbp:component
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ConcreteObserver
ConcreteSubject
Observer
Subject
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gptkbp:describedBy
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gptkb:Design_Patterns:_Elements_of_Reusable_Object-Oriented_Software
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gptkbp:example
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gptkb:C#_events_and_delegates
gptkb:Model-View-Controller_(MVC)
Java's java.util.Observer
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gptkbp:firstDescribed
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gptkb:GoF_book_(1994)
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https://www.w3.org/2000/01/rdf-schema#label
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Observer pattern
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gptkbp:notableFor
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gptkb:.NET_event_model
gptkb:JavaScript_event_listeners
gptkb:Java_Swing_event_model
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gptkbp:pattern
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Behavioral
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gptkbp:patternParticipants
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ConcreteObserver
ConcreteSubject
Observer
Subject
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gptkbp:problemSolved
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One-to-many dependency between objects
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gptkbp:purpose
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Decouple subject and observers
Define a one-to-many dependency so that when one object changes state, all its dependents are notified and updated automatically
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gptkbp:relatedTo
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gptkb:Mediator_pattern
Event listener
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gptkbp:solvedBy
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When one object changes state, all its dependents are notified and updated automatically
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gptkbp:supportsLanguage
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gptkb:Java
gptkb:JavaScript
gptkb:Python
gptkb:C#
gptkb:C++
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gptkbp:UMLRepresentation
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Class diagram with Subject and Observer interfaces
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gptkbp:usedIn
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Object-oriented programming
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gptkbp:bfsParent
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gptkb:MVC_(Model-View-Controller)
gptkb:Mediator_pattern
gptkb:RxJS
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gptkbp:bfsLayer
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5
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