Predicates and sorting in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a predicate that filters names starting with "A".

iOS Swift

let predicate = NSPredicate(format: "name BEGINSWITH [1]")

Drag options to blanks, or click blank then click option'

A'A'

B"A"

C"a"

DA

Attempts:

3 left

💡 Hint

Common Mistakes

Using single quotes instead of double quotes.

Not quoting the letter at all.

Using lowercase 'a' which won't match uppercase names.

The predicate format requires the string "A" to be in double quotes to match names starting with uppercase A.

2fill in blank

medium

Complete the code to sort an array of strings in ascending order.

iOS Swift

let sortedNames = names.sorted(by: { $0 [1] $1 })

Drag options to blanks, or click blank then click option'

A<

B>

C==

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' which sorts in descending order.

Using '==' which does not sort.

Using '>=' which is not a valid sorting comparator.

Using '<' sorts the array in ascending order alphabetically.

3fill in blank

hard

Fix the error in the predicate format to filter ages greater than 18.

iOS Swift

let predicate = NSPredicate(format: "age [1] 18")

Drag options to blanks, or click blank then click option'

A==

B=

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' instead of '==' or '>'.

Using '<' which filters ages less than 18.

Using '==' which filters only age exactly 18.

The '>' operator correctly filters for ages greater than 18.

4fill in blank

hard

Fill both blanks to create a predicate filtering names containing "John" and sort them descending.

iOS Swift

let predicate = NSPredicate(format: "name CONTAINS[c] [1]")
let sortedNames = names.sorted(by: { $0 [2] $1 })

Drag options to blanks, or click blank then click option'

A"John"

B<

C>

D"john"

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'john' which may not match case-insensitively without [c].

Using '<' which sorts ascending instead of descending.

Not quoting the string in the predicate.

The predicate uses "John" with quotes and the sorting uses '>' for descending order.

5fill in blank

hard

Fill all three blanks to create a dictionary of names and ages filtered by age > 20 and sorted by name ascending.

iOS Swift

let filtered = people.filter { $0.age [1] 20 }
let sorted = filtered.sorted(by: { $0.name [2] $1.name })
let nameAgeDict = Dictionary(uniqueKeysWithValues: sorted.map { ([3], $0.age) })

Drag options to blanks, or click blank then click option'

A>

B<

C$0.name

D$1.name

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' in filter which filters ages less than 20.

Using '>' in sort which sorts descending.

Using '$1.name' as key in map which is invalid.

Filter uses '>' for age > 20, sort uses '<' for ascending by name, and map uses '$0.name' as key.