In my Swift code below the goal is to delete a binary data by the corresponding var Int. The var Int is called counterImage. My code right now is causing a runtime error of counterImage
'Cannot convert value of type 'Int' to expected argument type 'TheBook''
What can I do to fix this? All the code is right here. You would have to add the images but after that you can just copy and paste the code.
import UIKit;import CoreData
class ViewController: UIViewController {
var counterImage = 1
override func viewDidLoad() {
super.viewDidLoad()
let gwen = UIImage(named: "h")
if let imageData = gwen.self?.pngData() {
helpImage.shareInstance.saveImage(data: imageData)
}
let gwen2 = UIImage(named: "hh")
if let imageData = gwen2.self?.pngData() {
helpImage.shareInstance.saveImage(data: imageData)
}
helpImage.shareInstance.deleteObject(user: counterImage)
}
}
class helpImage: UIViewController{
private class func getContext() -> NSManagedObjectContext {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
return appDelegate.persistentContainer.viewContext
}
static let shareInstance = helpImage()
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
func saveImage(data: Data) {
let imageInstance = TheBook(context: context)
imageInstance.pic = data
do {
try context.save()
} catch {
print(error.localizedDescription)
}
}
func deleteObject(user: TheBook) {
let context = helpImage.getContext()
let delete = NSBatchDeleteRequest(fetchRequest: TheBook.fetchRequest())
do {
try context.execute(delete)
} catch {
}
}
}
Related
In my swift code below the code saves an item in core data. The goal is to overwrite that item. I am getting a runtime error at
CoreDataHandler.changeName(user: fetchUser!\[indexNumber\], jessica: "jo")
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
I don't know how to wrap in the index number. The goal is it to print judo then jo
import UIKit;import CoreData
class ViewController: UIViewController {
var fetchUser: [UserInfo]? = nil
var indexNumber : Int = 0
override func viewDidLoad() {
super.viewDidLoad()
CoreDataHandler.saveObject2( name: "judo")
getText(textNo: indexNumber)
saveTheItem()
}
#objc func saveTheItem(){
CoreDataHandler.changeName(user: fetchUser![indexNumber], jessica: "jo")
}
func getText(textNo:Int) {
// first check the array bounds
let info = helpText.shareInstance.fetchText()
if info.count > textNo {
if let imageData = info[textNo].name
{
print(imageData)
} else {
// no data
print("data is empty Textss")
}
} else {
// image number is greater than array bounds
print("you are asking out of bounds")
}
}
}
class CoreDataHandler : NSManagedObject {
class func saveObject2( name: String) -> Bool {
let context = getContext()
let entity = NSEntityDescription.entity(forEntityName: "UserInfo", in: context)
let managedObject = NSManagedObject(entity: entity!, insertInto: context)
managedObject.setValue(name, forKey: "name")
do{
try context.save()
return true
}
catch {
return false
}
}
private class func getContext() -> NSManagedObjectContext{
let appD = UIApplication.shared.delegate as! AppDelegate
return appD.persistentContainer.viewContext
}
class func changeName(user: UserInfo,jessica : String) -> Bool
{
let context = getContext()
user.name = jessica
print(jessica)
do{
try context.save()
return true
}
catch{
return false
}
}
}
class helpText: UIViewController{
private class func getContext() -> NSManagedObjectContext {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
return appDelegate.persistentContainer.viewContext
}
static let shareInstance = helpText()
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
func saveName(data: String) {
let imageInstance = UserInfo(context: context)
imageInstance.name = data
do {
try context.save()
} catch {
print(error.localizedDescription)
}
}
func fetchText() -> [UserInfo] {
var fetchingImage = [UserInfo]()
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "UserInfo")
do {
fetchingImage = try context.fetch(fetchRequest) as! [UserInfo]
} catch {
print("Error while fetching the image")
}
return fetchingImage
}
}
No offense but your code is a mess.
And there is a big misunderstanding. Core Data records are unordered, there is no index. To update a record you have to fetch it by a known attribute, in your example by name, update it and save it back.
This is a simple method to do that. It searches for a record with the given name. If there is one, update the attribute with newName and save the record.
The code assumes that there is a NSManagedObject subclass UserInfo with implemented class method fetchRequest.
func changeName(_ name: String, to newName: String) {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let request : NSFetchRequest<UserInfo> = UserInfo.fetchRequest()
request.predicate = NSPredicate(format: "name == %#", name)
do {
let records = try context.fetch(request)
guard let foundRecord = records.first else { return }
foundRecord.name = newName
try context.save()
} catch {
print(error)
}
}
Regarding your confusing code:
Create CoreDataHandler as singleton (and it must not be a subclass of NSManagedObject). Move the Core Data related code from AppDelegate and the methods to read and write in this class.
IN my swift 5 code below the goal would be to fetch the first item from core data entity Info attribute username. I am attempting to d that right now I am getting a error at titleLabel.text = String(user![0]) stating
no exact matches in call to initializer
Somehow I know I will need to attach .username somehow but I dont know what to do next at this point.
class ViewController: UIViewController {
var user : [User]? = nil
var titleLabel = UILabel()
override func viewDidLoad() {
super.viewDidLoad()
user = CoredataHandler.fetchObject()
titleLabel.text = String(user![0])
}
}
class CoredataHandler : NSManagedObject {
private class func getContext() -> NSManagedObjectContext {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
return appDelegate.persistentContainer.viewContext
}
class func saveObject(username: String,password: String,tf: Bool) -> Bool{
let context = getContext()
let entity = NSEntityDescription.entity(forEntityName: "User", in: context)
let managedObject = NSManagedObject(entity: entity!, insertInto: context)
managedObject.setValue(username, forKey: "username")
managedObject.setValue(password, forKey: "password")
managedObject.setValue(tf, forKey: "tf")
do {
try context.save()
return true
} catch{
return false
}
}
class func fetchObject() -> [User]?
{
let context = getContext()
var user : [User]? = nil
do {
user = try context.fetch(User.fetchRequest())
return user
} catch {
return user
}
}
}
In my swift code I attempted to fetch core data string using a int. I have 2 classes my base class and my helper class. In my base class that is where the func attempting to fetch the string. That func has a error message at fetchImageTxt.text = String(data: imageData) stating Missing argument for parameter 'encoding' in call. Don't know how to resolve it.
BASE CLASS
class ViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
var fetchImageTxt = UITextField()
func getT(imageNo:Int) {
// first check the array bounds
let info = DataBaseHelper.shareInstance.fetchImage()
if info.count > imageNo {
// check if the data is available
if let imageData = info[imageNo].img {
fetchImageTxt.text = String(data: imageData)
} else {
// no data
print("data is empty")
}
} else {
// image number is greater than array bounds
print("you are asking out of bounds")
}
}
}
HELPER CLASS
class DataBaseHelper {
static let shareInstance = DataBaseHelper()
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
func fetchImage() -> [Info] {
var fetchingImage = [Info]()
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Info")
do {
fetchingImage = try context.fetch(fetchRequest) as! [Info]
} catch {
print("Error while fetching the image")
}
return fetchingImage
}
}
coreDataAttributes
I am using this line below :
self.present(activityViewController, animated: true, completion: nil)
And I am getting an error of - Use of unresolved identifier 'self'. Any ideas about how to resolve this? To me it looks as it it is subordinate to the class, but clearly doing something wrong. Any help would be appreciated.
import UIKit
import CoreData
class CoreDataViewController: UIViewController {
#IBOutlet weak var CoreDataView: UITableView!
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
var items:[Checkins]?
var btnnames = [""]
override func viewDidLoad() {
super.viewDidLoad()
// CoreDataView.dataSource = self
// CoreDataView.delegate = self
storeTranscription()
// Loads the current data
getTranscriptions()
// fetchCheckins()
let btn1name = btnnames[0]
let btn2name = btnnames[1]
let btn3name = btnnames[2]
let btn4name = btnnames[3]
let btn5name = btnnames[4]
let btn6name = btnnames[5]
// print(btnnames)
print(btn1name, btn2name, btn3name, btn4name, btn5name, btn6name)
}
#IBAction func export(_ sender: Any) {
exportDatabase()
}
#IBOutlet weak var Table_label: UILabel!
}
var CheckinDate: Date? = Date()
var fetchedStatsArray: [NSManagedObject] = []
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
func storeTranscription() {
//retrieve the entity that we just created
let entity = NSEntityDescription.entity(forEntityName: "Checkins", in: context)
let transc = NSManagedObject(entity: entity!, insertInto: context) as! Checkins
//set the entity values
transc.who = "Who"
transc.reason = "Reason for visit"
transc.date = CheckinDate
//save the object
do {
try context.save()
print("saved!")
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
} catch {
}
}
func getTranscriptions () {
//create a fetch request, telling it about the entity
let fetchRequest: NSFetchRequest<Checkins> = Checkins.fetchRequest()
do {
//go get the results
let searchResults = try context.fetch(fetchRequest)
fetchedStatsArray = searchResults as [NSManagedObject]
//I like to check the size of the returned results!
print ("num of results = \(searchResults.count)")
//You need to convert to NSManagedObject to use 'for' loops
for trans in searchResults as [NSManagedObject] {
//get the Key Value pairs (although there may be a better way to do that...
print("\(trans.value(forKey: "who")!)")
let mdate = trans.value(forKey: "CheckinDate") as! Date
print(mdate)
}
} catch {
print("Error with request: \(error)")
}
}
func exportDatabase() {
let exportString = createExportString()
saveAndExport(exportString: exportString)
}
func saveAndExport(exportString: String) {
let exportFilePath = NSTemporaryDirectory() + "Checkins.csv"
let exportFileURL = NSURL(fileURLWithPath: exportFilePath)
FileManager.default.createFile(atPath: exportFilePath, contents: NSData() as Data, attributes: nil)
//var fileHandleError: NSError? = nil
var fileHandle: FileHandle? = nil
do {
fileHandle = try FileHandle(forWritingTo: exportFileURL as URL)
} catch {
print("Error with fileHandle")
}
if fileHandle != nil {
fileHandle!.seekToEndOfFile()
let csvData = exportString.data(using: String.Encoding.utf8, allowLossyConversion: false)
fileHandle!.write(csvData!)
fileHandle!.closeFile()
let firstActivityItem = NSURL(fileURLWithPath: exportFilePath)
let activityViewController : UIActivityViewController = UIActivityViewController(
activityItems: [firstActivityItem], applicationActivities: nil)
activityViewController.excludedActivityTypes = [
UIActivity.ActivityType.assignToContact,
UIActivity.ActivityType.saveToCameraRoll,
UIActivity.ActivityType.postToFlickr,
UIActivity.ActivityType.postToVimeo,
UIActivity.ActivityType.postToTencentWeibo
]
self.present(activityViewController, animated: true, completion: nil)
}
}
func createExportString() -> String {
var checkinwho: String?
var checkinreason: String?
var export: String = NSLocalizedString("who, reason, date \n", comment: "")
for (index, itemList) in fetchedStatsArray.enumerated() {
if index <= fetchedStatsArray.count - 1 {
checkinwho = Checkins.value(forKey: "who") as! String?
checkinreason = itemList.value(forKey: "reason") as! String?
let Datevar = Checkins.value(forKey: "date") as! Date
let whostring = checkinwho
let reasonstring = checkinreason
let DateSting = "\(Datevar)"
export += "\(whostring!),\(reasonstring!),\(DateSting) \n"
}
}
print("This is what the app will export: \(export)")
return export
}
Remove the } on this line
#IBOutlet weak var Table_label: UILabel!
}
and put another } at the end of this file.
I am developing core data in my application.
I want to fetch name attribute from the core data.
class ViewController: UIViewController {
#IBOutlet weak var saveDataBtn:UIButton!
#IBOutlet weak var dataTxtField:UITextField!
#IBOutlet weak var dataLbl:UILabel!
var tasks: [Task] = []
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
#IBAction func saveDataBtnPressed(_sender : UIButton){
print("Save Data.")
let task = Task(context: context)
task.name = dataTxtField.text
(UIApplication.shared.delegate as! AppDelegate).saveContext()
getData()
}
func getData(){
do{
tasks = try context.fetch(Task.fetchRequest())
}catch{
print("Fetching Failed")
}
}
How can i get it?
Thanks,
In Swift 4, you can access the property directly.
do {
let tasks = try context.fetch(request)
for task in tasks {
print(task.name)
}
} catch let error {
print(error.localizedDescription)
}
UPDATED - How to delete and update an instance of an Entity.
Here are some ideas to organize the code to deal with the updating and deleting.
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
extension Task {
// to get an instance with specific name
class func instance(with name: String) -> Task? {
let request = Task.fetchRequest()
// create an NSPredicate to get the instance you want to make change
let predicate = NSPredicate(format: "name = %#", name)
request.predicate = predicate
do {
let tasks = try context.fetch(request)
return tasks.first
} catch let error {
print(error.localizedDescription)
return nil
}
}
// to update an instance with specific name
func updateName(with name: String) {
self.name = name
(UIApplication.shared.delegate as! AppDelegate).saveContext()
}
// to delete an instance
func delete() {
context.delete(self)
(UIApplication.shared.delegate as! AppDelegate).saveContext()
}
}
func howItWorks() {
guard let task = Task.instance(with: "a task's name") else { return }
task.updateName(with: "the new name")
task.delete()
}
In Swift 4.1 and 5. We will use NSPredicate to specify our required condition. NSFetchRequest has a property predicate will set our predicate here as follow.
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let fetch = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
let predicate = NSPredicate(format: "username = %#", argumentArray: ["John"]) // Specify your condition here
// Or for integer value
// let predicate = NSPredicate(format: "age > %d", argumentArray: [10])
fetch.predicate = predicate
do {
let result = try context.fetch(fetch)
for data in result as! [NSManagedObject] {
print(data.value(forKey: "username") as! String)
print(data.value(forKey: "password") as! String)
print(data.value(forKey: "age") as! String)
}
} catch {
print("Failed")
}