I am new at inheritance in swift and i'd like to understand how to create constructors in the best way.
I get an error Must call a designated initializer of the superclass 'Base'
class Base{
var id:String
var link:String
convenience init?(json: [String: Any]) {
guard let id = json["id"] as? String,
let link = json["link"] as? String else{
print("Failed Base Class Init!")
return nil
}
self.init(id: id, link: link)
}
init(id: String, link: String) {
self.id = id
self.link = link
}
}
class Image: Base{
func addImageToView(imageView: UIImageView){
Alamofire.request(self.link).responseImage { response in
if let img = response.result.value {
imageView.image = img
}
}
}
}
class Gallery:Base{
var images:[Image] = []
init?(json: [String: Any]){
super.init(json: json) // Here i get <- Must call a designated initializer of the superclass 'Base'
guard let tab = json["images"] as? [[String:Any]] else{
print("Failed Gallery Image Init!")
return nil
}
images = tab.compactMap{return Image(json: $0)}
}
}
How to do so that my class gallery creates a table of images from json and also initializes the id and link?
Make init?(json (also) a designated initializer
init?(json: [String: Any]) {
guard let id = json["id"] as? String,
let link = json["link"] as? String else{
print("Failed Base Class Init!")
return nil
}
self.id = id
self.link = link
}
And override it in the subclass
override init?(json: [String: Any]) {
super.init(json: json)
...
Related
Hi I am struggle to solve the problem dynamic protocol conformance in swift language. Please see code.
Protocol:
protocol Object {
init(by object: [String: Any])
}
Custom structs with protocol object conformance:
struct Tree: Object {
let treeName: String
init(by object: [String: Any]) {
self.treeName = object["tree"] as? String ?? "Notree"
}
}
struct Plant: Object {
let plantName: String
init(by object: [String : Any]) {
self.plantName = object["tree"] as? String ?? ""
}
}
The above code just fine until the object is [String: Any]. I can't use [[String: Any]] like below.
let coconut = ["tree":"Coconut"] // => This fine
let allTrees = [["tree":"Apple"],["tree":"Orange"],["tree":"Jakfruit"]] //=> Here is the problem
let aTree = Tree(by: coconut)
let bTree = Tree(by: ["data":allTrees])
let cTree = Plant(by: ["data":allTrees])
I can't use array of objects. So, I used to store objects in to key "data". Now I used extension: Array confirm protocol object.
extension Array: Object where Element == Object{
init(by object: [String : Any]) {
if let data = object["data"] as? [[String: Any]]{
self = data.map({ (object) -> Object in
// return Plant.init(by: object) // => Works, But I need dynamic confirmance
// return Tree.init(by: object) // => Works, But I need dynamic confirmance
return Object.init(by: object) //=> How can I do?
})
}else{
self = []
}
}
}
The return Object shows error Protocol type 'Object' cannot be instantiated. I tried lot to solve but not able.
Can someone suggest better idea or solution for this problem? Thank you in advance...
First, you should not use the constraint == Object. You want to say that not only [Object] is an Object, but also [Plant] and [Tree] are Objects too, right? For that, you should use the : Object constraint. Second, you can use Element.init to initialise a new Element of the array. Because of the constraint Element : Object, we know that a init(by:) initialiser exists:
extension Array: Object where Element: Object{
init(by object: [String : Any]) {
if let data = object["data"] as? [[String: Any]]{
self = data.map({ (object) in
return Element.init(by: object)
})
}else{
self = []
}
}
}
Usage:
let trees = [Tree](by: ["data": allTrees])
Here's what I think a more Swifty version of your code, making use of failable initialisers - initialisers that return nil when they fail to initialise the object:
protocol Object {
init?(by object: [String: Any])
}
struct Tree: Object {
let treeName: String
init?(by object: [String: Any]) {
if let treeName = object["tree"] as? String {
self.treeName = treeName
} else {
return nil
}
}
}
struct Plant: Object {
let plantName: String
init?(by object: [String : Any]) {
if let plantName = object["tree"] as? String {
self.plantName = plantName
} else {
return nil
}
}
}
extension Array: Object where Element: Object{
init?(by object: [String : Any]) {
if let data = object["data"] as? [[String: Any]]{
self = data.compactMap(Element.init)
}else{
return nil
}
}
}
I have a simple object which conforms to the NSCoding protocol.
import Foundation
class JobCategory: NSObject, NSCoding {
var id: Int
var name: String
var URLString: String
init(id: Int, name: String, URLString: String) {
self.id = id
self.name = name
self.URLString = URLString
}
// MARK: - NSCoding
required init(coder aDecoder: NSCoder) {
id = aDecoder.decodeObject(forKey: "id") as? Int ?? aDecoder.decodeInteger(forKey: "id")
name = aDecoder.decodeObject(forKey: "name") as! String
URLString = aDecoder.decodeObject(forKey: "URLString") as! String
}
func encode(with aCoder: NSCoder) {
aCoder.encode(id, forKey: "id")
aCoder.encode(name, forKey: "name")
aCoder.encode(URLString, forKey: "URLString")
}
}
I'm trying to save an instance of it in UserDefaults but it keeps failing with the following error.
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Attempt to insert non-property list object for key jobCategory'
This is the code where I'm saving in UserDefaults.
enum UserDefaultsKeys: String {
case jobCategory
}
class ViewController: UIViewController {
#IBAction func didTapSaveButton(_ sender: UIButton) {
let category = JobCategory(id: 1, name: "Test Category", URLString: "http://www.example-job.com")
let userDefaults = UserDefaults.standard
userDefaults.set(category, forKey: UserDefaultsKeys.jobCategory.rawValue)
userDefaults.synchronize()
}
}
I replaced the enum value to key with a normal string but the same error still occurs. Any idea what's causing this?
You need to create Data instance from your JobCategory model using JSONEncoder and store that Data instance in UserDefaults and later decode using JSONDecoder.
struct JobCategory: Codable {
let id: Int
let name: String
}
// To store in UserDefaults
if let encoded = try? JSONEncoder().encode(category) {
UserDefaults.standard.set(encoded, forKey: UserDefaultsKeys.jobCategory.rawValue)
}
// Retrieve from UserDefaults
if let data = UserDefaults.standard.object(forKey: UserDefaultsKeys.jobCategory.rawValue) as? Data,
let category = try? JSONDecoder().decode(JobCategory.self, from: data) {
print(category.name)
}
Old Answer
You need to create Data instance from your JobCategory instance using archivedData(withRootObject:) and store that Data instance in UserDefaults and later unarchive using unarchiveTopLevelObjectWithData(_:), So try like this.
For Storing data in UserDefaults
let category = JobCategory(id: 1, name: "Test Category", URLString: "http://www.example-job.com")
let encodedData = NSKeyedArchiver.archivedData(withRootObject: category, requiringSecureCoding: false)
let userDefaults = UserDefaults.standard
userDefaults.set(encodedData, forKey: UserDefaultsKeys.jobCategory.rawValue)
For retrieving data from UserDefaults
let decoded = UserDefaults.standard.object(forKey: UserDefaultsKeys.jobCategory.rawValue) as! Data
let decodedTeams = NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(decoded) as! JobCategory
print(decodedTeams.name)
Update Swift 4, Xcode 10
I have written a struct around it for easy access.
//set, get & remove User own profile in cache
struct UserProfileCache {
static let key = "userProfileCache"
static func save(_ value: Profile!) {
UserDefaults.standard.set(try? PropertyListEncoder().encode(value), forKey: key)
}
static func get() -> Profile! {
var userData: Profile!
if let data = UserDefaults.standard.value(forKey: key) as? Data {
userData = try? PropertyListDecoder().decode(Profile.self, from: data)
return userData!
} else {
return userData
}
}
static func remove() {
UserDefaults.standard.removeObject(forKey: key)
}
}
Profile is a Json encoded object.
struct Profile: Codable {
let id: Int!
let firstName: String
let dob: String!
}
Usage:
//save details in user defaults...
UserProfileCache.save(profileDetails)
Hope that helps!!!
Thanks
Swift save Codable object to UserDefault with #propertyWrapper
#propertyWrapper
struct UserDefault<T: Codable> {
let key: String
let defaultValue: T
init(_ key: String, defaultValue: T) {
self.key = key
self.defaultValue = defaultValue
}
var wrappedValue: T {
get {
if let data = UserDefaults.standard.object(forKey: key) as? Data,
let user = try? JSONDecoder().decode(T.self, from: data) {
return user
}
return defaultValue
}
set {
if let encoded = try? JSONEncoder().encode(newValue) {
UserDefaults.standard.set(encoded, forKey: key)
}
}
}
}
enum GlobalSettings {
#UserDefault("user", defaultValue: User(name:"",pass:"")) static var user: User
}
Example User model confirm Codable
struct User:Codable {
let name:String
let pass:String
}
How to use it
//Set value
GlobalSettings.user = User(name: "Ahmed", pass: "Ahmed")
//GetValue
print(GlobalSettings.user)
Save dictionary Into userdefault
let data = NSKeyedArchiver.archivedData(withRootObject: DictionaryData)
UserDefaults.standard.set(data, forKey: kUserData)
Retrieving the dictionary
let outData = UserDefaults.standard.data(forKey: kUserData)
let dict = NSKeyedUnarchiver.unarchiveObject(with: outData!) as! NSDictionary
Based on Harjot Singh answer. I've used like this:
struct AppData {
static var myObject: MyObject? {
get {
if UserDefaults.standard.object(forKey: "UserLocationKey") != nil {
if let data = UserDefaults.standard.value(forKey: "UserLocationKey") as? Data {
let myObject = try? PropertyListDecoder().decode(MyObject.self, from: data)
return myObject!
}
}
return nil
}
set {
UserDefaults.standard.set(try? PropertyListEncoder().encode(newValue), forKey: "UserLocationKey")
}
}
}
Here's a UserDefaults extension to set and get a Codable object, and keep it human-readable in the plist (User Defaults) if you open it as a plain text file:
extension Encodable {
var asDictionary: [String: Any]? {
guard let data = try? JSONEncoder().encode(self) else { return nil }
return try? JSONSerialization.jsonObject(with: data) as? [String : Any]
}
}
extension Decodable {
init?(dictionary: [String: Any]) {
guard let data = try? JSONSerialization.data(withJSONObject: dictionary) else { return nil }
guard let object = try? JSONDecoder().decode(Self.self, from: data) else { return nil }
self = object
}
}
extension UserDefaults {
func setEncodableAsDictionary<T: Encodable>(_ encodable: T, for key: String) {
self.set(encodable.asDictionary, forKey: key)
}
func getDecodableFromDictionary<T: Decodable>(for key: String) -> T? {
guard let dictionary = self.dictionary(forKey: key) else {
return nil
}
return T(dictionary: dictionary)
}
}
If you want to also support array (of codables) to and from plist array, add the following to the extension:
extension UserDefaults {
func setEncodablesAsArrayOfDictionaries<T: Encodable>(_ encodables: Array<T>, for key: String) {
let arrayOfDictionaries = encodables.map({ $0.asDictionary })
self.set(arrayOfDictionaries, forKey: key)
}
func getDecodablesFromArrayOfDictionaries<T: Decodable>(for key: String) -> [T]? {
guard let arrayOfDictionaries = self.array(forKey: key) as? [[String: Any]] else {
return nil
}
return arrayOfDictionaries.compactMap({ T(dictionary: $0) })
}
}
If you don't care about plist being human-readable, it can be simply saved as Data (will look like random string if opened as plain text):
extension UserDefaults {
func setEncodable<T: Encodable>(_ encodable: T, for key: String) throws {
let data = try PropertyListEncoder().encode(encodable)
self.set(data, forKey: key)
}
func getDecodable<T: Decodable>(for key: String) -> T? {
guard
self.object(forKey: key) != nil,
let data = self.value(forKey: key) as? Data
else {
return nil
}
let obj = try? PropertyListDecoder().decode(T.self, from: data)
return obj
}
}
(With this second approach, you don't need the Encodable and Decodable extensions from the top)
Well, investigated several similar topics here, done everything as suggested, but my computed property "previousUserData" returns me nil, when trying to cast the decoded object to my type. What's wrong?
#objc class PreviousUserData: NSObject, NSCoding {
var name: String
var phone: String
var email: String
func encode(with aCoder: NSCoder) {
aCoder.encode(name, forKey: "name")
aCoder.encode(phone, forKey: "phone")
aCoder.encode(email, forKey: "email")
}
required convenience init?(coder aDecoder: NSCoder) {
guard
let name = aDecoder.decodeObject(forKey: "name") as? String,
let phone = aDecoder.decodeObject(forKey: "phone") as? String,
let email = aDecoder.decodeObject(forKey: "email") as? String
else {
return nil
}
self.init(name: name, phone: phone, email: email)
}
init(name: String, phone: String, email: String) {
self.name = name
self.phone = phone
self.email = email
}
}
unarchived returns me nil, but data for key "userdata" is exists
var previousUserData: PreviousUserData? {
get {
if let object = UserDefaults.standard.object(forKey: "userdata") as? Data {
let unarchived = NSKeyedUnarchiver.unarchiveObject(with: object) as? PreviousUserData
return unarchived
}
return nil
}
set {
let encodedData: Data = NSKeyedArchiver.archivedData(withRootObject: previousUserData as Any)
UserDefaults.standard.setValue(encodedData, forKey: "userdata")
}
}
Actually you can't get valid data because the setter is wrong. You have to save newValue rather than previousUserData.
This is an slightly optimized version
var previousUserData: PreviousUserData? {
get {
guard let data = UserDefaults.standard.data(forKey: "userdata") else { return nil }
return NSKeyedUnarchiver.unarchiveObject(with: data) as? PreviousUserData
}
set {
guard let newValue = newValue else { return }
let encodedData = NSKeyedArchiver.archivedData(withRootObject: newValue)
UserDefaults.standard.set(encodedData, forKey: "userdata")
}
}
NSCoding is pretty heavy. In this case I'd recommend to use Codable to serialize the data as JSON or Property List. It gets rid of #objc, class and NSObject and reduces the entire code to
struct PreviousUserData : Codable {
var name: String
var phone: String
var email: String
}
var previousUserData: PreviousUserData? {
get {
guard let data = UserDefaults.standard.data(forKey: "userdata") else { return nil }
return try? JSONDecoder().decode(PreviousUserData.self, from: data)
}
set {
guard let newValue = newValue, let encodedData = try? JSONEncoder().encode(newValue) else { return }
UserDefaults.standard.set(encodedData, forKey: "userdata")
}
}
Is it possible to create optional initialization parameters in Swift so I can create an object from JSON with the values returned from the API call, but then when I'm saving that object later I can also save the downloaded UIImage for one of the urls I got before.
Example:
class Story: NSObject, NSCoding {
var id: Int?
var title, coverImageURL: String?
var coverImage: UIImage?
required init?(anId: Int?, aTitle: String?, aCoverImageURL: String?) {
self.id = anId
self.title = aTitle
self.coverImageURL = aCoverImageURL
}
convenience init?(json: [String: Any]) {
let id = json["id"] as? Int
let title = json["title"] as? String
let coverImageURL = json["cover_image"] as? String
self.init(
anId: id,
aTitle: title,
aCoverImageURL: coverImageURL,
)
}
Then Later I want to save objects to memory
//MARK: Types
struct PropertyKey {
static let id = "id"
static let title = "title"
static let coverImageURL = "coverImageURL"
static let coverImage = "coverImage"
}
//MARK: NSCoding
func encode(with aCoder: NSCoder) {
aCoder.encode(id, forKey: PropertyKey.id)
aCoder.encode(title, forKey: PropertyKey.title)
aCoder.encode(coverImageURL, forKey: PropertyKey.coverImageURL)
aCoder.encode(coverImage, forKey: PropertyKey.coverImage)
}
required convenience init?(coder aDecoder: NSCoder) {
guard let id = aDecoder.decodeObject(forKey: PropertyKey.id) as? Int else {
os_log("Unable to decode the id for a Story object.", log: OSLog.default, type: .debug)
return nil
}
guard let title = aDecoder.decodeObject(forKey: PropertyKey.title) as? String else {
os_log("Unable to decode the title for a Story object.", log: OSLog.default, type: .debug)
return nil
}
let coverImageURL = aDecoder.decodeObject(forKey: PropertyKey.coverImageURL) as? String
let coverImage = aDecoder.decodeObject(forKey: PropertyKey.coverImage) as? UIImage
self.init(
anId: id,
aTitle: title,
aCoverImageURL: coverImageURL,
coverImage: coverImage,
)
}
Does this make sense? I want to be able to save a Story object as soon as I get the response from the API, but later when I save the story to memory, I want to be able to save the fetched UIImage for the coverImage.
How would I do that?
I'm not sure why no one took the easy points on this answer, but the answer is to simply make your properties optionals, and then you can set them with a value, or nil. You can also create convenience initializers that automatically set certain values to nil if you want. So, using my app as an example, I have a model that gets built from an API call. that model has values like id, created_at, etc that don't exist until a record is saved to the server, but I create objects locally, store them, and eventually send them to the server, so I need to be able to set the above values only when creating an object from JSON, so here is what I did:
class Story: NSObject, NSCoding {
var id: Int?
var title, coverImageURL: String?
var coverImage: UIImage?
required init?(anId: Int?, aTitle: String?, aCoverImageURL: String?) {
self.id = anId
self.title = aTitle
self.coverImageURL = aCoverImageURL
}
convenience init?(json: [String: Any]) {
let id = json["id"] as? Int
let title = json["title"] as? String
let coverImageURL = json["cover_image"] as? String
self.init(
anId: id,
aTitle: title,
aCoverImageURL: coverImageURL,
)
}
convenience init?(aTitle: String, aCoverImage: UIImage?) {
let title = aTitle
let subtitle = aSubtitle
let coverImage = aCoverImage
let isActive = activeStatus
self.init(
anId: nil,
aTitle: title,
aCoverImageURL: nil,
aCoverImage: coverImage,
)
}
As you can see, I only set two of the values when I'm creating an object locally, and the other values are just set to nil. To allow a value to be set to nil, just make it an optional when setting it. Simple!
I am trying to save my object's array to array.plist but I get the following error:
Thread 1: signal SIGABRT error
My object class looks like this:
class Note {
// MARK: Properties
var title: String
var photo: UIImage?
var text: String
// MARK: Initialization
init?(title: String, photo: UIImage?, text: String) {
// Initialize stored properties.
self.title = title
self.photo = photo
self.text = text
// Initialization should fail if there is no name or if the rating is negative.
if title.isEmpty{
return nil
}
}
func encodeWithCoder(aCoder: NSCoder!) {
aCoder.encodeObject(title, forKey:"title")
aCoder.encodeObject(text, forKey:"text")
aCoder.encodeObject(photo, forKey:"photo")
}
init (coder aDecoder: NSCoder!) {
self.title = aDecoder.decodeObjectForKey("title") as! String
self.text = aDecoder.decodeObjectForKey("text") as! String
self.photo = aDecoder.decodeObjectForKey("photo") as! UIImage
}
}
In the controller, I try to save the array with the Notes object like this:
notes = [Notes]()
notes.append(note)
let paths = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory,NSSearchPathDomainMask.AllDomainsMask, true)
let path: AnyObject = paths[0]
let arrPath = path.stringByAppendingString("/array.plist")
NSKeyedArchiver.archiveRootObject(notes, toFile: arrPath)
Not all the properties in your class are not optional, yet when you retrieve them from the plist, you are unwrapping all of them. This might cause your code to crash.
For example, if the photo is nil and you saved the object, when you are retrieving it, you are unwrapping it self.photo = aDecoder.decodeObjectForKey("photo") as! UIImage, which will crash if you did not save anything there.
Try removing the unwrapping and check again for your crash. Even if this was not the cause of your crash, it will cause a crash at some point.
If this does not fix your problem, please paste the complete error log so it is a bit more clear what is happening.
For swift 5. You can save an array of custom classes to a .plist file that inherits from NSObject and NSSecureCoding.
If we create a custom class called Person:
import Foundation
class Person: NSObject, NSSecureCoding {
//Must conform to NSSecureCoding protocol
public class var supportsSecureCoding: Bool { return true } //set to 'true'
//just some generic things to describe a person
private var name:String!
private var gender:String!
private var height:Double!
//used to create a new instance of the class 'Person'
init(name:String, gender:String, height:Double) {
super.init()
self.name = name
self.gender = gender
self.height = height
}
//used for NSSecureCoding:
func encode(with coder: NSCoder) {
coder.encode(name, forKey: "name") //encodes the name to a key of 'name'
coder.encode(gender, forKey: "gender")
coder.encode(height, forKey: "height")
}
//used for NSSecureCoding:
required init?(coder: NSCoder) {
super.init()
self.name = (coder.decodeObject(forKey: "name") as! String)
self.gender = (coder.decodeObject(forKey: "gender") as! String)
self.height = (coder.decodeObject(forKey: "height") as! Double)
}
//created just to print the data from the class
public override var description: String { return String(format: "name=%#,gender=%#,height%f", name, gender, height) }
}
Now we can create functions to save and load from a .plist file in the ViewController class:
We need to gather data from the directory system of the device:
func documentsDirectory()->String {
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let documentsDirectory = paths.first!
return documentsDirectory
}
func dataFilePath ()->String{
return self.documentsDirectory().appendingFormat("/your_file_name_here.plist")
}
function to save the array:
func saveData(_ people:[Person]) {
let archiver = NSKeyedArchiver(requiringSecureCoding: true)
archiver.encode(people, forKey: "your_file_name_here")
let data = archiver.encodedData
try! data.write(to: URL(fileURLWithPath: dataFilePath()))
}
function to load the array:
func loadData() -> [Person] {
let path = self.dataFilePath()
let defaultManager = FileManager()
var arr = [Person]()
if defaultManager.fileExists(atPath: path) {
let url = URL(fileURLWithPath: path)
let data = try! Data(contentsOf: url)
let unarchiver = try! NSKeyedUnarchiver(forReadingFrom: data)
//Ensure the unarchiver is required to use secure coding
unarchiver.requiresSecureCoding = true
//This is where it is important to specify classes that can be decoded:
unarchiver.setClass(Person.classForCoder(), forClassName: "parentModule.Person")
let allowedClasses =[NSArray.classForCoder(),Person.classForCoder()]
//Finally decode the object as an array of your custom class
arr = unarchiver.decodeObject(of: allowedClasses, forKey: "your_file_name_here") as! [Person]
unarchiver.finishDecoding()
}
return arr
}
In the ViewController class:
override func viewDidLoad() {
super.viewDidLoad()
let testPerson = Person(name: "Bill", gender: "Male", height: 65.5)
let people:[Person] = [testPerson]
//Save the array
saveData(people)
//Load and print the first index in the array
print(loadData()[0].description)
}
Output:
[name=Bill,gender=Male,height=65.5000000]