How to remove a prefix from a string

Swift version: 5.10

Paul Hudson @twostraws May 28th 2019

Swift’s string have a built-in hasPrefix() method that returns true if the string starts with specific letters, but they don’t have a way to remove those letters if they exist.

Fortunately, we can fill that gap with an extension on String that combines hasPrefix() with dropFirst(), which will check whether the prefix exists and remove it in one go:

extension String {
    func deletingPrefix(_ prefix: String) -> String {
        guard self.hasPrefix(prefix) else { return self }
        return String(self.dropFirst(prefix.count))
    }
}