Deinitializers for cleanup in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a deinitializer in Swift?

A deinitializer is a special method called automatically just before an instance of a class is deallocated. It is used to perform cleanup tasks like freeing resources.

beginner

How do you declare a deinitializer in a Swift class?

You declare a deinitializer using the keyword deinit followed by curly braces. It has no parameters and no return type.<br><br>Example:<br>deinit {<br> // cleanup code<br>}

intermediate

When is the deinitializer called in Swift?

The deinitializer is called automatically when the last strong reference to a class instance is removed, just before the instance's memory is freed.

intermediate

Can structs or enums have deinitializers in Swift?

No, only classes can have deinitializers because structs and enums are value types and do not use reference counting.

beginner

Why is it important to use deinitializers for cleanup?

Deinitializers help release resources like file handles, network connections, or observers to avoid memory leaks and keep the app efficient.

Which keyword is used to define a deinitializer in Swift?

A deinit

B init

C destroy

D cleanup

The keyword deinit is used to define a deinitializer in Swift.

When is a deinitializer called?

A When the instance is created

B When a method is called

C When the program starts

D When the instance is about to be deallocated

A deinitializer is called automatically just before an instance is deallocated.

Which Swift types can have deinitializers?

A Classes only

B Structs only

C Enums only

D Classes, structs, and enums

Only classes can have deinitializers because they are reference types.

What is a common use of deinitializers?

A To initialize properties

B To create new instances

C To clean up resources like files or network connections

D To define methods

Deinitializers are used to clean up resources before an instance is destroyed.

Can you call a deinitializer manually in Swift?

A Yes, anytime

B No, it is called automatically

C Only inside the class

D Only from subclasses

Deinitializers are called automatically by Swift when the instance is deallocated.

Explain what a deinitializer is and when it runs in Swift.

Think about what happens when an object is no longer needed.

Describe why only classes have deinitializers and not structs or enums.

Consider how memory management differs between these types.