NEW: Master Swift design patterns with my latest book! >>

How to read names in a string using NSLinguisticTagger

Written by Paul Hudson    @twostraws

Foundation has a built-in class to parse strings of text, and it includes some useful options to extra names of people, places, organizations, and more.

To try it out, consider this string:

let text = "Apple Computer was established in Cupertino by Steve Jobs, Steve Wozniak, and Ronald Wayne."

That contains a company name, a place name, and three names of people all in one, and we can use NSLinguisticTagger to pull them all out.

First you create a linguistic tagger and tell it to look for the names of things inside that text string:

let tagger = NSLinguisticTagger(tagSchemes: [.nameType], options: 0)
tagger.string = text

Next you create the range to scan. This is done using the older NSRange type, like this:

let range = NSRange(location: 0, length: text.utf16.count)

Third, you tell NSLinguisticTagger what it should look for and how it should scan. One useful option here is .joinNames, which means it will return “Steve Jobs” as a single name rather than as two individual names:

let options: NSLinguisticTagger.Options = [.omitPunctuation, .omitWhitespace, .joinNames]
let tags: [NSLinguisticTag] = [.personalName, .placeName, .organizationName]

Finally, you tell NSLinguisticTagger to enumerate the tags in the input string, filter out any that aren’t in the tags array we’re looking for, convert the NSRange back to a Swift range, then print out each match:

tagger.enumerateTags(in: range, unit: .word, scheme: .nameType, options: options) { tag, tokenRange, stop in
    if let tag = tag, tags.contains(tag) {
        if let range = Range(tokenRange, in: text) {
            let name = text[range]
            print("\(name): \(tag)")
        }
    }
}

That will find the company, organization, and three people names in our string – nice!

Available from iOS 5.0

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.

Become a Swift guru

I wrote a book called Pro Swift that's dedicated to helping you master the Swift language, and it includes seven hours of video demonstrating each technique!

Click here to visit the Hacking with Swift store >>