Swift (Mobile Dev) 3

Question 1

What Swift mechanism lets you handle errors thrown by a function?

Accepted Answer

do-try-catch

Answer

A `do-try-catch` block calls a throwing function with `try` and catches any Error value in `catch` clauses.

Question 2

In Core Data, which class represents a managed object's schema definition?

Accepted Answer

NSEntityDescription

Answer

NSEntityDescription describes an entity's name, attributes, and relationships in the Core Data model.

Question 3

Which SwiftUI view modifier is used to respond to a value change and execute a side effect?

Accepted Answer

.onChange(of:)

Answer

.onChange(of:) triggers a closure whenever the specified value changes, making it ideal for reactive side effects.

Question 4

What is the result type of `try?` when the called function throws an error in Swift?

Accepted Answer

nil (Optional wrapping the type)

Answer

Using `try?` converts a throwing expression to an Optional; a thrown error produces nil instead of propagating.

Question 5

Which Xcode instrument is best for detecting retain cycles and memory leaks in a Swift app?

Accepted Answer

Leaks

Answer

The Leaks instrument traces object allocations and identifies cycles where memory is never freed.

Swift Practice Test