snake_case to camelCase Swift Decodable

customEnumerationDecoding.swift

import UIKit

enum InteractionCode: String, Decodable {
    case PROCEED, abort, tryOtherNetwork, TRY_OTHER_ACCOUNT, RETRY, RELOAD, VERIFY

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()

        let jsonString = try container.decode(String.self)
        var camelCasedString = String()
        for (index, stringComponent) in jsonString.lowercased().split(separator: "_").enumerated() {
            if index == 0 {
                camelCasedString += stringComponent
            } else {
                camelCasedString += stringComponent.capitalized
            }
        }

        if let code = InteractionCode(rawValue: camelCasedString) {
            self = code
        } else {
            let context = DecodingError.Context(codingPath: container.codingPath, debugDescription: "Unable to find enumeration case for " + jsonString)
            throw DecodingError.typeMismatch(Self.self, context)
        }
    }
}

// MARK: - Run

struct TestJson: Decodable {
    var code: InteractionCode
}

let json = "{ \"code\": \"TRY_OTHE_NETWORK\" }".data(using: .utf8)!
let decoded = try! JSONDecoder().decode(TestJson.self, from: json)
print(decoded)