MakingScienceFictionFact MakingScienceFictionFact - 4 months ago 36
iOS Question

How to use persist & retrieve an NSCoding compliant object to app Document directory in Swift 3?

Here's a NSCoding compliant object. I would like to save and recover it from the app's documents directory in Swift 3. I imagine it's a save method and recover method. How is this done?

import Foundation

class Book: NSObject, NSCoding {
var title: String
var author: String
var pageCount: Int
var categories: [String]
var available: Bool

init(title:String, author: String, pageCount:Int, categories:[String],available:Bool) {
self.title = title
self.author = author
self.pageCount = pageCount
self.categories = categories
self.available = available
}

// MARK: NSCoding
required convenience init?(coder: NSCoder) {

let title = coder.decodeObject(forKey: "title") as! String
let author = coder.decodeObject(forKey: "author")as! String
let categories = coder.decodeObject(forKey: "categories") as! [String]
let available = coder.decodeBool(forKey: "available")
let pageCount = coder.decodeInteger(forKey: "pageCount")

self.init(title:title, author:author,pageCount:pageCount,categories: categories,available:available)
}

func encode(with: NSCoder) {
with.encode(self.title, forKey: "title")
with.encode(self.author, forKey: "author")
with.encode(Int32(self.pageCount), forKey: "pageCount")
with.encode(self.categories, forKey: "categories")
with.encode(self.available, forKey: "available")
}
}


Thank You!

dan dan
Answer

Saving:

// Get documents directory
if let docs = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first {

    // Append your file name to the directory path
    let path = (docs as NSString).appendingPathComponent("filename")

    // Archive your object to a file at that path
    NSKeyedArchiver.archiveRootObject(yourObject, toFile: path)
}

Loading:

// Get documents directory
if let docs = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first {

    // Append your file name to the directory path
    let path = (docs as NSString).appendingPathComponent("filename")

    // Unarchive your object from the file
    let yourObject = NSKeyedUnarchiver.unarchiveObject(withFile: path) as? Book

    // do whatever with yourObject
}
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