kyle-c
11/19/2017 - 11:57 AM

Save data with UserDefaults

Few lines of code to save data using NSUserDefaults

Tags: NSUserDefaults - UserDefaults - Persistence - nsuserdefaults - userdefaults - persistence

CustomObjects.md
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1. With custom objects

Actually, you will need to archive the custom object into NSData then save it to user defaults and retrieve it from user defaults and unarchive it again. You can archive it like this

let teams = [Team(id: 1, name: "team1", shortname: "t1"), Team(id: 2, name: "team2", shortname: "t2")]

var userDefaults = UserDefaults.standard
let encodedData: Data = NSKeyedArchiver.archivedData(withRootObject: teams)
userDefaults.set(encodedData, forKey: "teams")
userDefaults.synchronize()

and unarchive it like this

let decoded  = userDefaults.object(forKey: "teams") as! Data
let decodedTeams = NSKeyedUnarchiver.unarchiveObject(with: decoded) as! [Team]

But if you just did that you will get .Team encodeWithCoder:]: unrecognized selector sent to instance

You will have to make Team conform to NSCoding just like this

class Team: NSObject, NSCoding {
    var id: Int
    var name: String
    var shortname: String


    init(id: Int, name: String, shortname: String) {
        self.id = id
        self.name = name
        self.shortname = shortname

    }

    required convenience init(coder aDecoder: NSCoder) {
        let id = aDecoder.decodeInteger(forKey: "id")
        let name = aDecoder.decodeObject(forKey: "name") as! String
        let shortname = aDecoder.decodeObject(forKey: "shortname") as! String
        self.init(id: id, name: name, shortname: shortname)
    }

    func encode(with aCoder: NSCoder) {
        aCoder.encode(id, forKey: "id")
        aCoder.encode(name, forKey: "name")
        aCoder.encode(shortname, forKey: "shortname")
    }
}

@see: http://stackoverflow.com/questions/29986957/save-custom-objects-into-nsuserdefaults

NSUserDefaults.swift
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let myVar = "myValue"
let userDefaults = UserDefaults.standard

// Saving
userDefaults.set(myVar, forKey: "myVar")
userDefaults.synchronize()

// Retriving
if let myVar = userDefaults.value(forKey: "myVar") {
        //do something here when myVar exists
    } else {
        //myVar not exists
}