How to run a case-insensitive search for one string inside another

Paul Hudson    October 26th 2018    @twostraws

You can search for one string inside another using the range(of:) method, like this:

let string = "The rain in Spain"
let range1 = string.range(of: "rain")

That returns an optional string index: if the word was found it will say where it was found, otherwise it will be nil.

However, range(of:) does a case-sensitive search by default, which means it will match “rain” but not “Rain” or “RAIN”. If you want a case-insensitive search you need to provide an extra parameter called options, passing it .caseInsensitive:

let range2 = string.range(of: "rain", options: .caseInsensitive)

That returns the same optional value depending on what was found, so you can wrap the whole thing in an if let to see whether a match was found:

if let range3 = string.range(of: "rain", options: .caseInsensitive) {
    // match
} else {
    // no match
}

Available from iOS 8.0

Did this solution work for you? Please pass it on!

Tweet

Other people are reading…

• How to concatenate strings to make one joined string
• How to load a string from a website URL
• How to parse a sentence using NSLinguisticTagger
• How to measure a string for Objective-C code
• Replacing text in a string using replacingOccurrences(of:)

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.