Read and Write Codable Models from the JSON file inside FileManager. 🎉

FileUtility.swift

//
//  FileUtility.swift
//  TravelApp
//
//  Created by Anand Nimje on 13/04/20.
//  Copyright © 2020 Anand. All rights reserved.
//

import Foundation

enum FileUtility<Value: Codable>{
    
    /// Add Files Name here
    enum Files: CustomStringConvertible {
        case airport
        case hotelist
        
        var description: String{
            switch self {
            case .airport:
                return "AirportList"
            case .hotelist:
                return "HotelCityList"
            }
        }
    }
    case fileName(Files)
}

extension FileUtility {
    
    @discardableResult
    func saveValue(_ model: Value) -> Bool{
        guard case .fileName(let file) = self else {
            return false
        }
        do {
            return try FileUtility.save(jsonObject: model.self, toFilename: file.description)
        } catch {
            return false
        }
    }
    
    var loadValue: Value?{
        guard case .fileName(let file) = self else {
            return nil
        }
        do {
            return try FileUtility.loadJSON(withFilename: file.description) as? Value
        } catch {
            return nil
        }
    }
}

/// Uses
/// Fetch Model
///
/// `let files = FileUtility<[AirPortCity]>.fileName(.airport).loadFile`
///
/// Save Model
///
/// `FileUtility<[AirPortCity]>.fileName(.airport).saveValue(values.airportCity ?? [])`
///

//MARK: - Decoder & Encoder operations
private extension FileUtility{
    
    static func loadJSON(withFilename filename: String) throws -> Any? {
        let fileManager = FileManager.default
        let urls = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
        if let url = urls.first {
            var fileURL = url.appendingPathComponent(filename)
            fileURL = fileURL.appendingPathExtension("json")
            let data = try Data(contentsOf: fileURL)
            let jsonObject = try JSONDecoder().decode(Value.self, from: data)
            return jsonObject
        }
        return nil
    }
    
    static func save(jsonObject: Value, toFilename filename: String) throws -> Bool{
        let fileManager = FileManager.default
        let urls = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
        if let url = urls.first {
            var fileURL = url.appendingPathComponent(filename)
            fileURL = fileURL.appendingPathExtension("json")
            let data = try JSONEncoder().encode(jsonObject)
            
            //Checking file is available or now
            guard fileManager.fileExists(atPath: fileURL.path) else {
                /// Create new file here
                return fileManager.createFile(atPath: fileURL.path, contents: data, attributes: nil)
            }
            try data.write(to: fileURL, options: [.atomicWrite])
            return true
        }
        return false
    }
}