Convert a Custom Object to Data to Be Saved in Nsuserdefauts

Convert a custom object to Data to be saved in NSUserDefauts

The issue there. is that you are mixing up Codable with NSCoding. To use NSKeyedArchiver's archivedData method you need to have a class that conforms to NSCoding. In you case you have a structure that conforms to Codable so you need to use JSONEncoder encode method. Note: Your equatable method declaration was wrong:

struct BallPark: Codable, Equatable  {
    static func == (lhs: Self, rhs: Self) -> Bool {
        return lhs.id == rhs.id
    }
    let id: String
    let name: String?
    let location: VenueCoordinates?
    let mapEnabled: Bool?
    let facilityStatus: String?
}

---

struct VenueCoordinates: Codable {
    let latitude: String?
    let longitude: String?
    
    var lat: Double? {
        guard let latitud = latitude else { return nil}
        return Double(latitud)
    }
    var lon: Double? {
        guard let longitude = longitude else { return nil}
        return Double(longitude)
    }
}

---

let bestBallParkToSave = BallPark.init(id: "1", name: "Steve", location: .init(latitude: "20.0", longitude: "40.0"), mapEnabled: true, facilityStatus: "a status")

do {
    let encodedBestBallPark = try JSONEncoder().encode(bestBallParkToSave)
    UserDefaults.standard.set(encodedBestBallPark, forKey: "favoriteBallPark")
    if let ballParkData = UserDefaults.standard.data(forKey: "favoriteBallPark") {
        let loadedBallPark = try JSONDecoder().decode(BallPark.self, from: ballParkData)
        print(loadedBallPark)  // BallPark(id: "1", name: Optional("Steve"), location: Optional(VenueCoordinates(latitude: Optional("20.0"), longitude: Optional("40.0"))), mapEnabled: Optional(true), facilityStatus: Optional("a status"))
    }
} catch {
     print(error)
}

---

You can also make your life easier extending UserDefaults and create customs encoding and decoding methods:

extension UserDefaults {
    func decodeObject<T: Decodable>(forKey defaultName: String, using decoder: JSONDecoder = .init()) throws -> T {
        try decoder.decode(T.self, from: data(forKey: defaultName) ?? .init())
    }
    func encode<T: Encodable>(_ value: T, forKey defaultName: String, using encoder: JSONEncoder = .init()) throws {
        try set(encoder.encode(value), forKey: defaultName)
    }
}

---

Usage:

let bestBallParkToSave = BallPark(id: "1", name: "Steve", location: .init(latitude: "20.0", longitude: "40.0"), mapEnabled: true, facilityStatus: "a status")
do {

    try UserDefaults.standard.encode(bestBallParkToSave, forKey: "favoriteBallPark")
    let loadedBallPark: BallPark = try UserDefaults.standard.decodeObject(forKey: "favoriteBallPark")
    print(loadedBallPark)  // BallPark(id: "1", name: Optional("Steve"), location: Optional(VenueCoordinates(latitude: Optional("20.0"), longitude: Optional("40.0"))), mapEnabled: Optional(true), facilityStatus: Optional("a status"))
    
} catch {
     print(error)
}

Save custom objects into NSUserDefaults

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")

and unarchive it like this

let decoded  = userDefaults.data(forKey: "teams")
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")
    }
}

how can store custom objects in NSUserDefaults

First you create custom class Like below.

CustomObject.h

#import <Foundation/Foundation.h>

@interface CustomObject : NSObject<NSCoding>

@property(strong,nonatomic)NSString *name;

@end 

CustomObject.m

#import "CustomObject.h"

@implementation CustomObject



- (void)encodeWithCoder:(NSCoder *)encoder {
    //Encode properties, other class variables, etc
    [encoder encodeObject:self.name forKey:@"name"];

}

- (id)initWithCoder:(NSCoder *)decoder {
    if((self = [super init])) {
        //decode properties, other class vars
        self.name = [decoder decodeObjectForKey:@"name"];

    }
    return self;
}

Then create CustomObject class object and store in NSUserDefaults

Stored your object like this

CustomObject *object =[CustomObject new];
object.name = @"test";

NSMutableArray *arr = [[NSMutableArray alloc]init];
[arr  addObject:object];

NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:arr];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:encodedObject forKey:@"storeObject"];
[defaults synchronize];

get custom object from NSUserDefaults like this

 NSData *storedEncodedObject = [defaults objectForKey:@"storeObject"];
        NSArray *arrStoreObject = [NSKeyedUnarchiver unarchiveObjectWithData:storedEncodedObject];
        for (int i=0; i<arrStoreObject.count; i++)
        {
            CustomObject *storedObject = [arrStoreObject objectAtIndex:i];
            NSLog(@"%@",storedObject.name);

        }

Swift saving and retrieving custom object from UserDefaults

Swift 4 or later

You can once again save/test your values in a Playground

---

UserDefaults need to be tested in a real project. Note: No need to force synchronize. If you want to test the coding/decoding in a playground you can save the data to a plist file in the document directory using the keyed archiver. You need also to fix some issues in your class:

---

class Person: NSObject, NSCoding {
    let name: String
    let age: Int
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
    required init(coder decoder: NSCoder) {
        self.name = decoder.decodeObject(forKey: "name") as? String ?? ""
        self.age = decoder.decodeInteger(forKey: "age")
    }
    func encode(with coder: NSCoder) {
        coder.encode(name, forKey: "name")
        coder.encode(age, forKey: "age")
    }
}

---

Testing:

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        do {
            // setting a value for a key
            let newPerson = Person(name: "Joe", age: 10)
            var people = [Person]()
            people.append(newPerson)
            let encodedData = try NSKeyedArchiver.archivedData(withRootObject: people, requiringSecureCoding: false)
            UserDefaults.standard.set(encodedData, forKey: "people")
            // retrieving a value for a key
            if let data = UserDefaults.standard.data(forKey: "people"),
                let myPeopleList = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? [Person] {
                myPeopleList.forEach({print($0.name, $0.age)})  // Joe 10
            }                    
        } catch {
            print(error)
        }
        
    }
}

How to store custom objects in NSUserDefaults

On your Player class, implement the following two methods (substituting calls to encodeObject with something relevant to your own object):

- (void)encodeWithCoder:(NSCoder *)encoder {
    //Encode properties, other class variables, etc
    [encoder encodeObject:self.question forKey:@"question"];
    [encoder encodeObject:self.categoryName forKey:@"category"];
    [encoder encodeObject:self.subCategoryName forKey:@"subcategory"];
}

- (id)initWithCoder:(NSCoder *)decoder {
    if((self = [super init])) {
        //decode properties, other class vars
        self.question = [decoder decodeObjectForKey:@"question"];
        self.categoryName = [decoder decodeObjectForKey:@"category"];
        self.subCategoryName = [decoder decodeObjectForKey:@"subcategory"];
    }
    return self;
}

Reading and writing from NSUserDefaults:

- (void)saveCustomObject:(MyObject *)object key:(NSString *)key {
    NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:object];
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:encodedObject forKey:key];
    [defaults synchronize];

}

- (MyObject *)loadCustomObjectWithKey:(NSString *)key {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *encodedObject = [defaults objectForKey:key];
    MyObject *object = [NSKeyedUnarchiver unarchiveObjectWithData:encodedObject];
    return object;
}

Code shamelessly borrowed from: saving class in nsuserdefaults

How can I store an custom class as Data

Define a custom object which conforms to Codable. A simple example:

struct MyObject: Codable {
    var something: String
}

And when you want to save it to UserDefaults, just encode it:

do {
    let encoded = try JSONEncoder().encode(MyObject(something: "String"))
    UserDefaults.standard.set(encoded, forKey: "kSavedObject")
} catch {
    print(error)
}

If you want to retrieve it, you can use decode:

if let data = UserDefaults.standard.data(forKey: "kSavedObject") {
    do {
        let myRetrievedObject = try JSONDecoder().decode(MyObject.self, from: data)
    } catch {
        print(error)
    }
}

How to save a multi-leveled custom object to NSUserDefault's?

All the objects (Instructor, Class, and Student) need to adopt and implement the NSCoding protocol. See this post for an implentation. As @uchuugaka said though, it sounds like NSUserDefaults isn't the place to store this data.

You could still serialize the data to disk, but just write it to a separate file. Apple's Archives and Serializations Programming Guide is good reading to learn the basics of this method.

If the object graph you want to save is going to be more complex and you require searching and querying the object graph, e.g. finding the number of students with studentMoney >= 50 with lastName beginning with 'A', then you may want to look into Core Data. However, be aware that Core Data is an advanced framework so it does have a sizable learning curve.

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