ObjectDecoder: Turn dicts and arrays into structs and classes

This is some code I wrote for Asana that can apply a Decodable implementation to a nested collection. For example:

struct Person: Decodable {
  let name: String
}

let personDict = ["name": "Bob"]

let person = try ObjectDecoder.decode(Person.self, from: personDict)
// -> Person(name: "Bob")

Another possible use is to help migrate an old codebase from JSONSerialization to Codable for HTTP response parsing. You can port parsing code to Codable one object at a time, starting deep in the response and working your way out.

let apiResponse = "{\"data\": {\"person\": {\"name\": \"Bob\"}}}"
let json = try! JSONSerialization.jsonObject(with: apiResponse.data(using: .utf8)!)
let personData = ((json as! NSDictionary)["data"] as! NSDictionary)["person"] as! NSDictionary
let person = try ObjectDecoder.decode(Person.self, from: personData)

Installation

In the interest of getting this code out in public, I skimped on polishing this repo, so you have two options:

Option 1: Copy the Swift file into your codebase.
Option 2: Open a pull request adding a Package.swift file and moving ObjectDecoder.swift to the right place. Then, install using Swift Package Manager. 🙂

Regarding maintenance

It's not clear to me how many people need this. I'm responsive to pull requests but will not necessarily make updates proactively.