ISBN

A Swift package for parsing ISBN strings into a type-safe structure. The package supports both ISBN-10 and ISBN-13 and can output normalized strings in a variety of formats. Besides validating the checksum digit, the parser also divides the ISBN into its constituent parts – country code, registration group, registrant, and publication – making it possible, for example, to compare ISBNs from the same publisher.

Installation

ISBN is distributed with the Swift Package Manager. Add the following code to your Package.swift manifest.

let package = Package(
    ...
    dependencies: [
        .package(url: "https://github.com/iansampson/ISBN", .branch("main"))
    ],
    ...
)

Usage

To parse an ISBN, simply initialize an ISBN object with a string:

let isbn = try ISBN("978-0-8223-5656-1")

The constructor accepts strings in either ISBN-10 or ISBN-13, with or without hyphenation (although the hyphens must fall between valid ISBN components).

You can access the individual components as properties:

isbn.countryCode // .bookland
isbn.registrationGroup.value // 0
isbn.registrant.value // 8223
isbn.publication.value // 5656

To re-encode the ISBN as a normalized string, use one of the following methods:

isbn.string // 978-0-8223-5656-1
isbn.string(format: .isbn10, hyphenated: false) // 0822356562

If format is set to .isbn10 and the ISBN is prefixed with 979 (i.e. the “musicland” country code), the second method returns nil. Since all ISBN-10s are implicitly prefixed with 978, there is no way to encode a musical ISBN using only 10 digits. In all other cases, the method returns a string.