Shorthand argument names ($0, $1) in Swift

Introduction

Shorthand argument names let you write shorter, simpler code when using closures. They save time by avoiding naming each argument.

When you want to quickly sort a list without writing a full closure.

When you need to transform items in a list with a simple operation.

When filtering a list based on a quick condition.

When you want to keep your code clean and easy to read for small closures.

Syntax

Swift

list.method { $0, $1 in
    // use $0 for first argument
    // use $1 for second argument
}

$0 is the first argument, $1 is the second, and so on.

You don't have to write the argument names or types explicitly.

Examples

Sorts numbers using $0 and $1 as the two items to compare.

Swift

let numbers = [3, 1, 2]
let sorted = numbers.sorted { $0 < $1 }

Transforms each name to uppercase using $0 as the current item.

Swift

let names = ["Anna", "Bob", "Cindy"]
let uppercased = names.map { $0.uppercased() }

Filters scores to keep only those 60 or above using $0 as the score.

Swift

let scores = [85, 42, 90, 75]
let passed = scores.filter { $0 >= 60 }

Sample Program

This program shows sorting, mapping, and filtering using shorthand argument names $0 and $1.

Swift

let fruits = ["apple", "banana", "cherry"]

// Sort fruits alphabetically
let sortedFruits = fruits.sorted { $0 < $1 }
print("Sorted fruits:", sortedFruits)

// Make all fruits uppercase
let upperFruits = fruits.map { $0.uppercased() }
print("Uppercase fruits:", upperFruits)

// Filter fruits that start with 'b'
let bFruits = fruits.filter { $0.hasPrefix("b") }
print("Fruits starting with 'b':", bFruits)

Important Notes

Shorthand arguments only work inside closures.

Use them for short closures to keep code clean.

For complex closures, naming arguments can improve clarity.

Summary

Shorthand argument names like $0 and $1 let you write shorter closures.

$0 is the first argument, $1 the second, and so on.

They make simple tasks like sorting, mapping, and filtering easier and cleaner.