How to read a single character from a string

Swift version: 5.0

Paul Hudson    @twostraws    May 28th 2019

Swift’s strings are stored in a specific way that stops you from indexing into then easily. In fact, reading one letter from part-way through the string means starting at the beginning of the string and counting through letters until you find the one you want, so if you try reading all the characters in the string this way you could accidentally create extremely slow code.

However, if you only need to read one or two letters, here’s a simple extension on String that will help:

extension String {
    subscript(i: Int) -> String {
        return String(self[index(startIndex, offsetBy: i)])
    }
}

With that place in place, you can write myString[15] to read the 16th letter.

Available from iOS 8.0

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