Shorthand argument names ($0, $1) in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the squares of numbers using shorthand argument names.

Swift

let numbers = [1, 2, 3, 4]
let squares = numbers.map { $[1] * $[1] }
print(squares)

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

A2

B1

C0

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using $1 when there is only one argument.

Using variable names instead of shorthand arguments.

The shorthand argument $0 refers to the first argument passed to the closure, which is each element in the array.

2fill in blank

medium

Complete the code to filter numbers greater than 3 using shorthand argument names.

Swift

let numbers = [1, 2, 3, 4, 5]
let filtered = numbers.filter { $[1] > 3 }
print(filtered)

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

A0

B1

Cindex

Dself

Attempts:

3 left

💡 Hint

Common Mistakes

Using $1 when only one argument is passed.

Using variable names instead of shorthand arguments.

The closure passed to filter takes each element as the first argument, accessible via $0.

3fill in blank

hard

Fix the error in the code by using the correct shorthand argument name to sort pairs by their second value.

Swift

let pairs = [("a", 3), ("b", 1), ("c", 2)]
let sorted = pairs.sorted { $[1].1 < $[2].1 }
print(sorted)

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A$0, $1

B0, 1

C1, 2

D$1, $0

Attempts:

3 left

💡 Hint

Common Mistakes

Using numeric literals instead of shorthand arguments.

Swapping $0 and $1 incorrectly.

The closure for sorted takes two arguments, accessible as $0 and $1. We compare their second elements with .1.

4fill in blank

hard

Fill both blanks to create a closure that adds two numbers using shorthand argument names.

Swift

let add = { $[1] + $[2] }
print(add(5, 7))

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

A$0

B$1

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using numeric literals instead of shorthand arguments.

Using the same shorthand argument for both blanks.

The closure takes two arguments, accessible as $0 and $1, which we add together.

5fill in blank

hard

Fill all three blanks to create a dictionary from an array of tuples using shorthand argument names.

Swift

let items = [("apple", 3), ("banana", 5), ("cherry", 2)]
let dict = Dictionary(uniqueKeysWithValues: items.map { ( $[1].0, $[2].1 ) })
print(dict)

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

A$0

B$1

Attempts:

3 left

💡 Hint

Common Mistakes

Using $1 when only one argument is passed.

Mixing up tuple element indices.

The map closure takes one argument (a tuple), accessible as $0. We use $0.0 for the key and $0.1 for the value.