[Solved] Which of the following is the correct way to register an observer in the Observer pattern?subject = Subject() observer = ConcreteObserver() # What code registers the observer? | LLD

LLD - Behavioral Design Patterns — Part 1

Which of the following is the correct way to register an observer in the Observer pattern?

subject = Subject()
observer = ConcreteObserver()
# What code registers the observer?

Asubject.addObserver(observer)

Bobserver.subscribe(subject)

Cobserver.register(subject)

Dsubject.attach(observer)

Step-by-Step Solution

Solution:

Step 1: Recall common Observer pattern method names
Typically, the subject has a method named attach or addObserver to register observers.
Step 2: Identify the most standard method
While addObserver is used in some languages, attach is the classic and widely accepted method name.
Final Answer:
subject.attach(observer) -> Option D
Quick Check:
Register observer = subject.attach(observer) [OK]

Quick Trick: Subject.attach(observer) is classic registration [OK]

Common Mistakes:

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Which of the following is the correct way to register an observer in the Observer pattern?