Swift Technology & Digital Applications 2

Question 1

Which Swift feature allows a function to accept a varying number of arguments of the same type?

Accepted Answer

Variadic parameters

Answer

Variadic parameters are declared with `...` after the type and let a function receive zero or more values of that type as an array.

Question 2

In Swift, what does the `@discardableResult` attribute do?

Accepted Answer

Suppresses the warning when a return value is ignored

Answer

`@discardableResult` tells the compiler not to warn when the caller ignores the function's return value.

Question 3

Which protocol must a Swift type conform to in order to be used as a dictionary key?

Accepted Answer

Hashable

Answer

Dictionary keys must conform to `Hashable`, which also implies `Equatable`, so the dictionary can compute and compare hash values.

Question 4

What is the purpose of Swift's `lazy` stored property modifier?

Accepted Answer

It defers initialization until the property is first accessed

Answer

`lazy` properties are not initialized until they are first accessed, which is useful for expensive computations or dependencies on self.

Question 5

In SwiftUI, which modifier is used to react to changes in a state value and perform a side effect?

Accepted Answer

.onChange

Answer

`.onChange(of:)` triggers a closure whenever the specified value changes, making it the correct choice for value-change side effects.

Swift Practice Test