How to transform a dictionary using mapValues()
Swift version: 5.6
Although dictionaries have a general map() method, they also have a specialized form of map() called mapValues() – it transforms just the values of the dictionary, leaving the keys untouched.
This extra method is useful because dictionaries can’t have duplicate keys, but if you’re only transforming the values from a dictionary then this is not a problem.
Let’s try it out on a dictionary containing the height in centimeters of various people:
let peopleMetric = ["Taylor": 178.0, "Justin": 175.0, "Ed": 173.0]If we want to convert those heights to inches without changing the keys, we can use mapValues() like this:
let peopleImperial = peopleMetric.mapValues { $0 / 2.54 }
SPONSORED Fernando's book will guide you in fixing bugs in three real, open-source, downloadable apps from the App Store. Learn applied programming fundamentals by refactoring real code from published apps. Hacking with Swift readers get a $10 discount!
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 8.0 – learn more in my book Pro Swift
Similar solutions…
- Showing dictionary definitions using UIReferenceLibraryViewController
- How to use map() to transform an array
- How to use compactMap() to transform an array
- What is a dictionary?
- How to specify default values for dictionary keys
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
