Cookbooks
Swift
Chapter 10. Data Formats and Serialization
Working with TOML

Swift:
Working with TOML

How to:

To start, you need a TOML parser. Swift doesn’t have a built-in one, so let’s use TOMLDecoder. Install it via Swift Package Manager and then serialize and deserialize TOML with ease.

import TOMLDecoder

let tomlString = """
title = "TOML Example"

[owner]
name = "Tom Preston-Werner"
dob = 1979-05-27T07:32:00Z
"""

struct Config: Codable {
    let title: String
    let owner: Owner
}

struct Owner: Codable {
    let name: String
    let dob: Date
}

let decoder = TOMLDecoder()
if let configData = tomlString.data(using: .utf8) {
    do {
        let config = try decoder.decode(Config.self, from: configData)
        print("Title: \(config.title), Owner: \(config.owner.name), DOB: \(config.owner.dob)")
    } catch {
        print("Error parsing TOML: \(error)")
    }
}

This code outputs:

Title: TOML Example, Owner: Tom Preston-Werner, DOB: 1979-05-27 07:32:00 +0000

Deep Dive

TOML was designed by Tom Preston-Werner, GitHub’s co-founder, as a more human-friendly alternative to formats like JSON or YAML. It aims for clarity, reducing the chances of misinterpretation by a human or machine. As for alternatives, YAML and JSON are the usual suspects, with YAML skewed towards human readability and JSON as the simpler machine-friendly option. When working with TOML in Swift, we don’t have a native parser. However, third-party libraries like TOMLDecoder facilitate easy conversion between TOML strings and Swift types, specifically via Codable protocols introduced in Swift 4 that streamlined serialization.

See Also

Working with JSONWorking with XML