Weekly Swift articles, podcasts and tips by John Sundell.

Usages of throwing functions

Published on 24 Apr 2018
Basics article available: Error Handling

A big benefit of using throwing functions for synchronous Swift APIs is that the caller can decide whether they want to treat the return value as optional (try?) or required (try).

func loadFile(named name: String) throws -> File {
    guard let url = urlForFile(named: name) else {
        throw File.Error.missing
    }

    do {
        let data = try Data(contentsOf: url)
        return File(url: url, data: data)
    } catch {
        throw File.Error.invalidData(error)
    }
}

let requiredFile = try loadFile(named: "AppConfig.json")

let optionalFile = try? loadFile(named: "UserSettings.json")