Foundation-free Swift/JSON processing.

SWON is a tiny set of Swift Macros that extend value types with simplified JSON processing without the need for Codable or the Foundation framework.

SWON should work on every supported Swift platform. Tested on Apple, Android, Linux, and Windows.

Dead easy. Attach the macro to any struct or enum:

import SWON
@SWON
enum Color {
	case red, green, blue
}
@SWON
struct Foobar {
	let numField: Int
	let stringArray: [String]
	let myDictionary: [String: [Double]]
	let innerStructs: [[CustomStruct]]
	let namedList: [Color]?
}

And you'll get a new initializer:

let foobar = try Foobar(fromJSON: """
{
"numField": 100,
"stringArray": ["one", "two", "three"]
	...
}
""")

SWON is part of an ongoing "fight" against Swift dependencies outside of the Apple ecosystem, whose goal is making my app, Passepartout, natively cross-platform with Swift.

If you only use Swift on Apple platforms, you won't find this package very useful, if at all. JSONEncoder and JSONDecoder offer such a thorough feature set that SWON doesn't even try to replace them.

Instead, it serves the single purpose of parsing complex value types with a tiny footprint, because it doesn't rely on Foundation. In fact, SWON doesn't even use Codable, thus making it a future candidate for Embedded Swift, where Codable is unavailable.

Last but not least, it was an entertaining exercise to get familiar with Swift Macros.

SWON uses the amazingly written cJSON parser (C) under the hood.

• Dictionary keys must be String.
• Optionals in collections (e.g. [Int?]) are not supported.

• Encode Swift to JSON (decode-only for now).
• Enums with associated types.
• Do not suppress errors inside an optional field (silently made nil).

Copyright (c) 2025 Davide De Rosa. All rights reserved.

This project is licensed under the MIT.

Twitter: @keeshux

Website: davidederosa.com, with my blog series on cross-platform Swift.