Save Encodable object to document directory and load as Decodable object.

JSONSerialization+SaveLoadToDocumentDirectory.swift

//
//  Created by Egzon Pllana on 28.12.21.
//

import Foundation

class FilesIOManager {

    // MARK: - Properties

    private static let jsonString = "json"
    private static let fileManager = FileManager.default
    private static let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)

    // MARK: - Methods

    /// Save Encodable Object
    /// - Parameters:
    ///   - object: Encodable object.
    ///   - filename: Object name.
    /// - Returns: Path url where object is saved.
    static func save(_ object: Encodable, filename: String) throws -> URL? {
        // Convert encodable object to dictionary string
        let userJsonToDictionary = try object.toDictionary()

        // Get file path url
        guard let url = urls.first else { return nil }
        var fileURL = url.appendingPathComponent(filename)
        fileURL = fileURL.appendingPathExtension(jsonString)

        // Write data to file url
        let data = try JSONSerialization.data(withJSONObject: userJsonToDictionary, options: [.prettyPrinted])
        try data.write(to: fileURL, options: [.atomicWrite])
        return fileURL
    }

    /// Load Decodable Object
    /// - Returns: Returns optional Decodable object
    static func load<T: Decodable>(_ type: T.Type, withFilename filename: String) throws -> T? {
        // Get file path url
        guard let url = urls.first else { return nil }
        var fileURL = url.appendingPathComponent(filename)
        fileURL = fileURL.appendingPathExtension(jsonString)

        // Get data from path url
        let contentData = try Data(contentsOf: fileURL)

        // Get json object from data
        let jsonObject = try JSONSerialization.jsonObject(with: contentData, options: [.mutableContainers, .mutableLeaves])

        // Convert json object to data type
        let jsonData = try JSONSerialization.data(withJSONObject: jsonObject, options: [])

        // Decode data to Decodable object
        let decoder = JSONDecoder()
        let decodedObject = try! decoder.decode(T.self, from: jsonData)

        return decodedObject
    }
}

// MARK: - Encodable to Dictionary

extension Encodable {
    /// Convert Encodable object to dictionary
    /// - Parameter encoder: JSONEncoder
    /// - Returns: dictionary [String: Any]
    func toDictionary(_ encoder: JSONEncoder = JSONEncoder()) throws -> [String: Any] {
        let data = try encoder.encode(self)
        let object = try JSONSerialization.jsonObject(with: data)
        guard let json = object as? [String: Any] else {
            let context = DecodingError.Context(codingPath: [], debugDescription: "Deserialized object is not a dictionary!")
            throw DecodingError.typeMismatch(type(of: object), context)
        }
        return json
    }
}