Swift version: 5.6
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.
SPONSORED Proxyman: A high-performance, native macOS app for developers to easily capture, inspect, and manipulate HTTP/HTTPS traffic. The ultimate tool for debugging network traffic, supporting both iOS and Android simulators and physical devices.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 2.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.