Swift version: 5.0
One of my favorite little gems in Cocoa Touch is called
NSCountedSet, and it's the most efficient way to count objects in a set. Here's the code:
let set = NSCountedSet() set.add("Bob") set.add("Charlotte") set.add("John") set.add("Bob") set.add("James") set.add("Sophie") set.add("Bob") print(set.count(for: "Bob"))
Now to how it works: a set is like an array, except each item can appear only once. If we used an array in the above code, it would contain seven objects: three Bobs, one Charlotte, one John, one James and one Sophie. If we used a Swift set in the above code, it would contain four objects: one Bob, one Charlotte, one John, one James and one Sophie – the set ensures each item appears only once.
Now for the twist:
NSCountedSet works similar to a set insofar as each object can appear only once, but it keeps track of how many times each item was added and removed. So, our counted set will have four objects in (like it would if it were a regular set), but
NSCountedSet has a
count(for:) method that will report back that Bob was added three times.
SPONSOR Tired of wasting time debugging your Swift app? Instabug’s SDK is here to help you minimize your debugging time by providing you with complete device details, network logs, and reproduction steps with every bug report. All data is attached automatically. It only takes a line of code to setup. Get started for free.
Available from iOS 2.0
Did this solution work for you? Please pass it on!
Other people are reading…
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.