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In Angular, why is it preferable to initiate Observable subscriptions inside the ngOnInit lifecycle hook rather than in the constructor?

easy🧠 Conceptual Q1 of 15
Angular - RxJS and Observables Fundamentals
In Angular, why is it preferable to initiate Observable subscriptions inside the ngOnInit lifecycle hook rather than in the constructor?
ABecause subscriptions in the constructor cause memory leaks automatically.
BBecause the constructor cannot access services injected via dependency injection.
CBecause Observables cannot be subscribed to outside lifecycle hooks.
DBecause <code>ngOnInit</code> is called after Angular has set all input properties, ensuring component readiness.
Step-by-Step Solution
Solution:

  1. Step 1: Understand Angular lifecycle

    The constructor runs before Angular sets input properties, so the component may not be fully initialized.

  2. Step 2: Role of ngOnInit

    ngOnInit is called after inputs are set, making it the ideal place to start subscriptions that depend on component inputs.

  3. Final Answer:

    Because ngOnInit is called after Angular has set all input properties, ensuring component readiness. -> Option D

  4. Quick Check:

    Subscriptions depend on initialized inputs [OK]
Quick Trick: Subscribe in ngOnInit after inputs are ready [OK]
Common Mistakes:
MISTAKES
  • Subscribing in constructor assuming inputs are ready
  • Believing Observables can't be subscribed outside lifecycle hooks
  • Thinking constructor subscriptions auto-manage memory

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