Load and store a Codable Class in file

AGCodableStorage.swift

//
//  AGCodableStorage.swift
//  BaseProject
//
//  Created by thirdeyes Infotech Pvt Ltd on 05/04/18.
//  Copyright © 2018 AshvinGudaliya. All rights reserved.
//

import UIKit

class AGCodableStorage: NSObject {
    
    fileprivate var directory: Directory = .caches
    fileprivate var fileName: FileName = .tempFiles
    
    fileprivate var fileUrl: URL {
        get{
            var searchPathDirectory: FileManager.SearchPathDirectory
            
            switch directory {
            case .documents:
                searchPathDirectory = .documentDirectory
            case .caches:
                searchPathDirectory = .cachesDirectory
            }
            
            if let url = FileManager.default.urls(for: searchPathDirectory, in: .userDomainMask).first {
                return url
            } else {
                fatalError("Could not create URL for specified directory!")
            }
        }
    }
    
    enum Directory {
        case documents
        case caches
    }
    
    enum FileName: String {
        case tempFiles = "Temps.json"
    }
    
    
    init(for directory: Directory, fileName: FileName){
        self.directory = directory
        self.fileName = fileName
        
        super.init()
    }

    /// Store an encodable struct to the specified directory on disk
    ///
    /// - Parameters:
    ///   - object: the encodable struct to store
    ///   - directory: where to store the struct
    ///   - fileName: what to name the file where the struct data will be stored
    func store<T: Encodable>(_ object: T) {
        let url = fileUrl.appendingPathComponent(fileName.rawValue, isDirectory: false)
        
        let encoder = JSONEncoder()
        do {
            let data = try encoder.encode(object)
            if FileManager.default.fileExists(atPath: url.path) {
                try FileManager.default.removeItem(at: url)
            }
            FileManager.default.createFile(atPath: url.path, contents: data, attributes: nil)
        } catch {
            fatalError(error.localizedDescription)
        }
    }
    
    /// Retrieve and convert a struct from a file on disk
    ///
    /// - Parameters:
    ///   - fileName: name of the file where struct data is stored
    ///   - directory: directory where struct data is stored
    ///   - type: struct type (i.e. Message.self)
    /// - Returns: decoded struct model(s) of data
    func retrieve<T: Decodable>(as type: T.Type) -> T {
        let url = fileUrl.appendingPathComponent(fileName.rawValue, isDirectory: false)
        
        if !FileManager.default.fileExists(atPath: url.path) {
            fatalError("File at path \(url.path) does not exist!")
        }
        
        if let data = FileManager.default.contents(atPath: url.path) {
            let decoder = JSONDecoder()
            do {
                let model = try decoder.decode(type, from: data)
                return model
            } catch {
                fatalError(error.localizedDescription)
            }
        } else {
            fatalError("No data at \(url.path)!")
        }
    }
    
    /// Remove all files at specified directory
    func clear(_ directory: Directory) {
        do {
            let contents = try FileManager.default.contentsOfDirectory(at: fileUrl, includingPropertiesForKeys: nil, options: [])
            for fileUrl in contents {
                try FileManager.default.removeItem(at: fileUrl)
            }
        } catch {
            fatalError(error.localizedDescription)
        }
    }
    
    /// Remove specified file from specified directory
    func remove() {
        let url = fileUrl.appendingPathComponent(fileName.rawValue, isDirectory: false)
        if FileManager.default.fileExists(atPath: url.path) {
            do {
                try FileManager.default.removeItem(at: url)
            } catch {
                fatalError(error.localizedDescription)
            }
        }
    }
    
    /// Returns BOOL indicating whether file exists at specified directory with specified file name
    var fileExists: Bool {
        let url = fileUrl.appendingPathComponent(fileName.rawValue, isDirectory: false)
        return FileManager.default.fileExists(atPath: url.path)
    }
}