Shorthand argument names ($0, $1) in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are shorthand argument names like $0 and $1 in Swift?

They are automatic names for closure parameters, used to refer to the first, second, etc., arguments without explicitly naming them.

beginner

How do you use $0 in a Swift closure?

Inside a closure, $0 refers to the first argument passed to the closure, allowing you to write shorter code without naming parameters.

beginner

Example: What does this Swift code print?<br><pre>let numbers = [1, 2, 3]
let doubled = numbers.map { $0 * 2 }
print(doubled)</pre>

It prints [2, 4, 6]. The map function uses $0 to refer to each number in the array and doubles it.

intermediate

Can you use $1 in a Swift closure? When?

Yes, $1 refers to the second argument passed to the closure. Use it when the closure takes two or more parameters.

beginner

Why might shorthand argument names be helpful?

They make code shorter and cleaner by removing the need to write explicit parameter names, especially in simple closures.

In Swift, what does $0 represent inside a closure?

A The closure itself

B The closure's return value

C The first argument passed to the closure

D The last argument passed to the closure

$0 is the shorthand name for the first argument passed to a closure.

Which of these is a valid use of shorthand argument names in Swift?

A array.map { $0 + 1 }

B array.map { first + 1 }

C array.map { $2 + 1 }

D array.map { $ }

$0 is valid for the first argument; $2 is invalid if closure has fewer arguments.

When should you use $1 in a Swift closure?

A Never, it's invalid

B Only when the closure has one parameter

C When you want the closure's return value

D When the closure has at least two parameters

$1 refers to the second parameter, so use it when the closure has two or more parameters.

What is the benefit of using shorthand argument names in Swift closures?

A Makes code shorter and easier to read for simple closures

B Improves program speed

C Allows naming parameters explicitly

D Prevents errors in closures

Shorthand argument names reduce code clutter and improve readability in simple closures.

Which of the following is NOT a valid shorthand argument name in Swift closures?

A $0

B $10

C $2

D $1

Swift supports shorthand argument names up to the number of parameters passed; $10 is invalid if closure has fewer than 11 parameters.

Explain how shorthand argument names like $0 and $1 work in Swift closures.

Think about how closures can be shorter without naming parameters.

Give an example of using $0 in a Swift closure and describe what it does.

Use a simple array operation like map.