ARC overview for memory management in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does ARC stand for in Swift?

ARC stands for Automatic Reference Counting. It helps manage memory by keeping track of how many references point to an object.

beginner

How does ARC decide when to free an object?

ARC frees an object when its reference count drops to zero, meaning no part of the code is using it anymore.

beginner

What is a strong reference in ARC?

A strong reference is the default way Swift keeps an object alive by increasing its reference count when assigned.

intermediate

What problem can strong reference cycles cause?

Strong reference cycles happen when two objects hold strong references to each other, preventing ARC from freeing them and causing memory leaks.

intermediate

How can you break a strong reference cycle in Swift?

You can use weak or unowned references to break strong reference cycles. These references do not increase the reference count.

What happens when an object's reference count reaches zero in ARC?

A The object is deallocated and memory is freed.

B The object is copied to a new memory location.

C The object is marked as read-only.

D Nothing happens; the object stays in memory.

When the reference count is zero, ARC automatically frees the object's memory.

Which type of reference increases an object's reference count in Swift ARC?

A Weak reference

B Unowned reference

C None of the above

D Strong reference

Strong references increase the reference count, keeping the object alive.

What keyword is used in Swift to declare a weak reference?

A unowned

B weak

C strong

D var

The 'weak' keyword declares a weak reference that does not increase the reference count.

Why are strong reference cycles problematic?

A They prevent ARC from freeing memory, causing leaks.

B They delete objects too early.

C They slow down the CPU.

D They cause the program to crash immediately.

Strong reference cycles keep objects alive forever, causing memory leaks.

Which reference type should you use when you know the referenced object will always exist during the reference's lifetime?

A strong

B weak

C unowned

D optional

Unowned references are used when the referenced object is expected to always exist while the reference exists.

Explain how ARC manages memory in Swift and what happens when an object's reference count changes.

Think about how Swift keeps track of who is using an object.

Describe what a strong reference cycle is and how to prevent it in Swift.

Consider how two friends holding hands tightly might never let go.