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 }TAKE YOUR SKILLS TO THE NEXT LEVEL If you like Hacking with Swift, you'll love Hacking with Swift+ – it's my premium service where you can learn advanced Swift and SwiftUI, functional programming, algorithms, and more. Plus it comes with stacks of benefits, including monthly live streams, downloadable projects, a 20% discount on all books, and free gifts!
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Available from iOS 8.0 – learn more in my book Pro Swift
Similar solutions…
- How to use map() to transform an array
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- What is a dictionary?
- How to specify default values for dictionary keys
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