Sorted and custom comparators in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the sorted() method do in Swift?

The sorted() method returns a new array with the elements sorted in ascending order by default.

beginner

How do you use a custom comparator with sorted(by:) in Swift?

You provide a closure that takes two elements and returns true if the first element should be ordered before the second, otherwise false.

beginner

Example: Sort an array of integers in descending order using sorted(by:).

Use <code>let sortedArray = array.sorted(by: { $0 > $1 })</code> to sort from highest to lowest.

intermediate

Why use a custom comparator instead of the default sorted()?

A custom comparator lets you define your own sorting rules, like sorting strings by length or sorting objects by a property.

intermediate

What is the type signature of the closure used in sorted(by:)?

The closure has type (Element, Element) -> Bool, where it compares two elements and returns true if the first should come before the second.

What does array.sorted() return in Swift?

A The original array sorted in place

B An error if the array is not sorted

C A Boolean indicating if the array is sorted

D A new array sorted in ascending order

sorted() returns a new sorted array and does not change the original.

Which closure signature is correct for sorted(by:)?

A (Element, Element) -> Bool

B (Element) -> Bool

C (Element, Element) -> Element

D (Element) -> Element

The closure compares two elements and returns true if the first should come before the second.

How do you sort an array of strings by their length in ascending order?

A array.sorted()

B array.sorted(by: { $0.count < $1.count })

C array.sorted(by: { $0 > $1 })

D array.sorted(by: { $0.count > $1.count })

Use a custom comparator comparing the count property to sort by length.

What happens if you use sorted(by: { $0 < $1 })?

A Causes a runtime error

B Sorts the array in descending order

C Sorts the array in ascending order

D Leaves the array unsorted

This comparator sorts elements from smallest to largest (ascending).

Can sorted(by:) be used to sort arrays of custom objects?

A Yes, by providing a closure comparing object properties

B No, only basic types can be sorted

C Only if the objects conform to <code>Comparable</code>

D Only if the array is mutable

You can sort custom objects by defining how to compare them in the closure.

Explain how to sort an array in Swift using a custom comparator.

Think about how you tell Swift the order you want.

Describe the difference between sorted() and sorted(by:).

One is simple, the other lets you decide the order.