In Objective C, when you call performSelector withObject afterDelay, does the passed object get retained until the selector is executed, and why does that matter for memory management?

Introduction / Context:
Objective C memory management rules, especially before full adoption of ARC, are a common source of interview questions. The performSelector withObject afterDelay method schedules a message to be sent later using the run loop. This question tests whether you know how the runtime manages the lifetime of the target and the argument object during the delay interval.

Given Data / Assumptions:

• We are using Objective C on Apple platforms with Foundation and UIKit or AppKit.
• The method performSelector:withObject:afterDelay: schedules a message on the run loop.
• The question concerns whether the argument object remains alive until the scheduled call occurs.

Concept / Approach:
When you schedule a selector with a delay, the runtime needs to ensure that both the target and the argument are still valid when the message is finally delivered. To achieve this, it retains these objects when scheduling the call and releases them after the selector has been invoked. This behavior prevents the object from being deallocated prematurely, which would otherwise lead to crashes when accessing deallocated memory.

Step-by-Step Solution:
Step 1: Consider what would happen if the runtime did not retain the object; if the caller later released it, the pointer stored for the delayed call might become invalid.Step 2: Apple designed performSelector:withObject:afterDelay: so that the run loop infrastructure retains the target and the argument at the time the call is scheduled.Step 3: When the delay expires, the run loop delivers the message, invoking the selector on the target with the argument.Step 4: After invocation, the runtime releases both the target and the argument, balancing the earlier retain and preserving memory management correctness.Step 5: This exact behavior is described in option A, which identifies that the objects are retained until execution finishes.

Verification / Alternative check:
Apple documentation and technical Q and A articles explain that the scheduled invocation retains the target and argument. Many memory management guidelines warn developers about potential retain cycles when using delayed selectors, because these implicit retains can keep objects alive longer than expected if they also strongly reference each other. This documentation confirms that option A is correct.

Why Other Options Are Wrong:
Option B is incorrect because if the object were not retained, delayed invocations would frequently crash when accessing freed memory. Option C is wrong because the Objective C runtime does not treat primitive values as retained objects; retention applies only to Objective C object references. Option D is false because this behavior is defined by the runtime and is not dependent on compiler optimization levels.

Common Pitfalls:
Developers sometimes forget that scheduling a delayed selector can extend the lifetime of objects and accidentally create retain cycles, especially when self is the target and also holds a strong reference to related objects. Another pitfall is assuming that cancelPreviousPerformRequestsWithTarget will always be called; if it is not, the objects may remain alive longer than expected. Understanding the retention behavior helps in designing correct and leak free code.

Final Answer:
Yes, the runtime retains the target and the object until the selector is performed and then releases them afterward.