How to convert a Substring to a String

Written by Paul Hudson    @twostraws

Swift has a dedicated Substring type (String.SubSequence) that is designed to hold slices of strings, which is a performance optimization: when you store part of a string in a different variable, Swift can simply point the substring at the parent string rather than copy all the data.

However, while substrings can be used in many of the same ways as regular strings, they aren’t the same – if you have a function that accepts a String as a parameter, you simply cannot send it a Substring.

To fix this, you can wrap your substring in a String initializer like this:

let quote = "The revolution will be Swift"
let substring = quote.dropFirst(23)
let realString = String(substring)

Available from iOS 8.0

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