Swift Tips

An extensive guide to sorting Arrays in Swift

Published on: April 7, 2021

When you're working with Arrays in Swift, it's likely that you'll want to sort them at some point. In Swift, there are two ways to sort an Array: Through the Comparable implementation for each element in your array By providing a closure to perform a manual/specialized comparison between elements If you have a homogenous array of elements, for example [String], you can rely on String's implementation of Comparable to sort an array of String in some sensible manner. There are two ways to sort an array of Comparable elements: var strings = ["Oh", "Hello", "World", "This", "Is", "An", "Unsorted", "Array"]...

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How to sort an Array based on a property of an element in Swift?

Published on: January 20, 2020

This post is a short demo of using Swift's sort() and sort(by:) methods. For a more comprehensive overview of sorting, and some background information on how Swift's sorting works I recommend you take a look at this updated post The easiest way to sort an Array in Swift is to use the sort method. This method is available for all Arrays that have Comparable elements and it sorts your array in place: var words = ["hello", "world", "this", "is", "a", "list", "of", "strings"] words.sort() // words is now ["a", "hello", "is", "list", "of", "strings", "this", "world"] This modifies the input...

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How to add an element to the start of an Array in Swift?

Published on: January 19, 2020

You can use Array's insert(_:at:) method to insert a new element at the start, or any other arbitrary position of an Array: var array = ["world"] array.insert("hello", at: 0) // array is now ["hello", "world"] Make sure that the position that you pass to the at: argument isn't larger than the array's current last index plus one. For example: // this is fine var array = ["hello"] array.insert("world", at: 1) // this will crash var array = ["hello"] array.insert("world", at: 2) If you have any questions about this tip, or if you have feedback for me, don't hesitate to reach...

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How to check if two date ranges overlap in Swift

Published on: January 17, 2020

Dates in Swift can be compared to each other. This allows you to check whether one date comes before or after another date: if dateOne > dateTwo { print("dateOne comes after dateTwo") } else if dateOne < dateTwo { print("dateOne comes before dateTwo") } else if dateOne == dateTwo { print("dateOne is equal to dateTwo") } You can also use dates in Swift to create ranges. And when you have one range, you can check whether it overlaps with another date. Let's look at an example: struct Meeting { let startDate: Date let endDate: Date } func doMeetingsOverlap(_ meetingOne: Meeting,...

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Remove instances of an object from an Array in Swift

Published on: January 10, 2020

Arrays in Swift are powerful and they come with many built-in capabilities. One of these capabilities is the ability to remove objects. If you want to remove a single, specific object from an Array and you know its index, you can use remove(at:) to delete that object: var array = [1, 2, 3] array.remove(at: 0) // array is now [2, 3] If you don't know the object's position in the Array and the Array's elements conform to Equatable, you can look up the first index of the object you're looking for with firstIndex(of:) and you can then proceed to delete...

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How to filter an Array in Swift?

Published on: January 9, 2020

When you have an Array of elements, and you want to drop all elements that don't match specific criteria from the Array, you're looking for Array's filter(isIncluded:) method. Let's say you have an array of words and you only want to keep the words that are longer than three characters: let words = ["hello", "world", "this", "is", "a", "list", "of", "strings"] let filtered = words.filter { word in return word.count >= 3 } // filtered is ["hello", "world", "this", "list", "strings"] The filter(isIncluded:) method takes a closure that is executed for every element in the source Array. If you return...

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Reversing an Array in Swift

Published on: January 1, 2020

You can reverse an Array, and any other Collection in Swift using the reverse method. For example var input = [1, 2, 3] print(input) // [1, 2, 3] input.reverse() print(input) // [3, 2, 1] The code above takes an array (input) and reverses it in-place using the reverse() method. This only works if your array is mutable. If you want to reverse an immutable array that's defined as let, or if you don't want to alter the original input you can use reversed() instead of reverse(): var input = [1, 2, 3] print(input) // [1, 2, 3] var reversed =...

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Find every other element in an array with Swift

Published on: June 30, 2015

Note: This blog post has been updated for Xcode 11 and Swift 5 👍🏼 There are times when you need to extract a subset of an array. For example, you might need to find all elements in an array at an odd index. Or maybe you need all items at an even index. In other words, you're looking for every "other" element in an array. This might seem like a non-trivial task and you may have tried this before using a for loop as follows: var itemsAtEvenIndices = [Int]() let allItems = [1, 2, 3, 4, 5, 6, 7] var...

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