NEW: Join my free 100 Days of SwiftUI challenge today! >>

How to convert a multidimensional array to a single-dimensional array

Swift version: 5.1

Paul Hudson    @twostraws   

If you have an array of arrays – for example, an array of an array of integers – you can convert it to a single, flat array by using the joined() method. Because Swift sends back an optimized type (FlattenSequence<[[YourType]]>, in this case), you might also want to add an array conversion for easier use.

For example, here’s an array of arrays of strings, such as you might find if you had one array for each class of students, grouped into a larger array to represent the whole school:

let classes = [
    ["Ash", "Brock", "Misty"],
    ["Gloria", "Piper", "Suzanne"],
    ["Picard", "Riker", "Troi"]
]

We can use joined() to get a single array of names like this:

let allStudents = classes.joined()

As noted, that will make allStudents an instance of FlattenSequence<[[String]]> rather than an array, so if you need to send it back from a method or want to subscript it you should convert it to an array first, like this:

let allStudents = Array(classes.joined())

That will set allStudents to an array containing Ash, Brock, Misty, Gloria, Piper, Suzanne, Picard, Riker, and Troi.

SAVE 20% ON iOS CONF SG The largest iOS conference in Southeast Asia is back in Singapore for the 5th time in January 2020, now with two days of workshops plus two days of talks on SwiftUI, Combine, GraphQL, and more! Save a massive 20% on your tickets by clicking on this link.

Available from iOS 8.0

Similar solutions…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!