All PatternsBehavioral
Observer
Defines a subscription mechanism to notify multiple objects about events.
Event systemsUI updatesPub/sub messaging
Understanding Observer
The Observer pattern defines a one-to-many dependency between objects. When one object changes state, all its dependents are notified automatically. Also known as Pub/Sub.
How It Works
Subject
Publisher
state: "old"
Observers
Observer A
Observer B
Observer C
Subject holds state
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Subject
Subject maintains state and list of observers.
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Basic Implementation
Simple subject with multiple observers:
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Real-World Example: Stock Market
Stock price notifications with traders and alert bots:
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