I am trying to check if certain entity has data, so I wrote this code I am not sure if my code correct.When I check my code I found that if there is a data I got the answer that "data exist", but if there is no data compiler ignore else statement. I cannot understand why this happen.
func entityIsEmpty()
{
let context = objAppDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>.init(entityName: "myEntity")
//do{
//result = try context.fetch(fetchRequest) as! [NSManagedObject]
result = fetchRequest as! [NSManagedObject] //ERROR
for data in result{
var obj = userNSObj()
obj.myObject = data.value(forKey: "myAttribute") as! String
myArray.append(obj)
if myArray != nil{
print("data exist")
}else{
print("data not exist")
}
}
//}catch{
//print("Failed")
//}
}
After the edit you messed up the code.
This checks if the fetched data array is empty and returns if the array is empty
func entityIsEmpty()
{
let context = objAppDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<myEntity>(entityName: "myEntity")
do {
let result = try context.fetch(fetchRequest)
if result.isEmpty {
print("data not exist")
return
} else {
print("data exist")
}
for data in result {
var obj = userNSObj()
obj.myObject = data.myAttribute
myArray.append(obj)
}
} catch {
print(error)
}
}
Related
Probably a stupid question, but I'm a beginner at this.
The below code is supposed to get book information from Google Books from a keyword search. It then goes through the results and checks if I have a matching ISBN in a Firebase database. It works, but currently can only search 40 books as that's the Google Books API maximum per search.
Fortunately, I can specify where to start the index and get the next 40 books to search as well. Unfortunately, I've been trying for hours to understand how the URLSession works. All the methods I've tried have shown me that the code after the URLSession block doesn't necessarily wait for the session to complete. So if I check if I've found any matches afterward, it might not even be done searching.
I suspect the answer is in completion handling, but my attempts so far have been unsuccessful. Below is my code with a URL setup to take various starting index values.
var startingIndex = 0
//encode keyword(s) to be appended to URL
let query = query.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)!
let url = "https://www.googleapis.com/books/v1/volumes?q=\(query)&&maxResults=40&startIndex=\(startingIndex)"
URLSession.shared.dataTask(with: URL(string: url)!) { (data, response, error) in
if error != nil {
print(error!.localizedDescription)
}else{
let json = try! JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [String: AnyObject]
if let items = json["items"] as? [[String: AnyObject]] {
//for each result make a book and add title
for item in items {
if let volumeInfo = item["volumeInfo"] as? [String: AnyObject] {
let book = Book()
//default values
book.isbn13 = "isbn13"
book.isbn10 = "isbn10"
book.title = volumeInfo["title"] as? String
//putting all authors into one string
if let temp = volumeInfo["authors"] as? [String] {
var authors = ""
for i in 0..<temp.count {
authors = authors + temp[i]
}
book.author = authors
}
if let imageLinks = volumeInfo["imageLinks"] as? [String: String] {
book.imageURL = imageLinks["thumbnail"]
}
//assign isbns
if let isbns = volumeInfo["industryIdentifiers"] as? [[String: String]] {
for i in 0..<isbns.count {
let firstIsbn = isbns[i]
if firstIsbn["type"] == "ISBN_10" {
book.isbn10 = firstIsbn["identifier"]
}else{
book.isbn13 = firstIsbn["identifier"]
}
}
}
//adding book to an array of books
myDatabase.child("listings").child(book.isbn13!).observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() {
if listings.contains(book) == false{
listings.append(book)
}
DispatchQueue.main.async { self.tableView.reloadData() }
}
})
myDatabase.child("listings").child(book.isbn10!).observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() {
if listings.contains(book) == false{
listings.append(book)
}
DispatchQueue.main.async { self.tableView.reloadData() }
}
})
}
}
}
}
SVProgressHUD.dismiss()
}.resume()
Below is my revised code:
func searchForSale(query: String, startingIndex: Int) {
directionsTextLabel.isHidden = true
tableView.isHidden = false
listings.removeAll()
DispatchQueue.main.async { self.tableView.reloadData() }
SVProgressHUD.show(withStatus: "Searching")
//clear previous caches of textbook images
cache.clearMemoryCache()
cache.clearDiskCache()
cache.cleanExpiredDiskCache()
let url = "https://www.googleapis.com/books/v1/volumes?q=\(query)&&maxResults=40&startIndex=\(startingIndex)"
URLSession.shared.dataTask(with: URL(string: url)!) { (data, response, error) in
if error != nil {
print(error!.localizedDescription)
}else{
var needToContinueSearch = true
let json = try! JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [String: AnyObject]
if json["error"] == nil {
let totalItems = json["totalItems"] as? Int
if totalItems == 0 {
SVProgressHUD.showError(withStatus: "No matches found")
return
}
if let items = json["items"] as? [[String: AnyObject]] {
//for each result make a book and add title
for item in items {
if let volumeInfo = item["volumeInfo"] as? [String: AnyObject] {
let book = Book()
//default values
book.isbn13 = "isbn13"
book.isbn10 = "isbn10"
book.title = volumeInfo["title"] as? String
//putting all authors into one string
if let temp = volumeInfo["authors"] as? [String] {
var authors = ""
for i in 0..<temp.count {
authors = authors + temp[i]
}
book.author = authors
}
if let imageLinks = volumeInfo["imageLinks"] as? [String: String] {
book.imageURL = imageLinks["thumbnail"]
}
//assign isbns
if let isbns = volumeInfo["industryIdentifiers"] as? [[String: String]] {
for i in 0..<isbns.count {
let firstIsbn = isbns[i]
//checks if isbns have invalid characters
let isImproperlyFormatted = firstIsbn["identifier"]!.contains {".$#[]/".contains($0)}
if isImproperlyFormatted == false {
if firstIsbn["type"] == "ISBN_10" {
book.isbn10 = firstIsbn["identifier"]
}else{
book.isbn13 = firstIsbn["identifier"]
}
}
}
}
//adding book to an array of books
myDatabase.child("listings").child(book.isbn13!).observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() {
if listings.contains(book) == false{
listings.append(book)
needToContinueSearch = false
}
DispatchQueue.main.async { self.tableView.reloadData() }
}
})
myDatabase.child("listings").child(book.isbn10!).observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() {
if listings.contains(book) == false{
listings.append(book)
needToContinueSearch = false
}
DispatchQueue.main.async { self.tableView.reloadData() }
return
}
if startingIndex < 500 {
if needToContinueSearch {
let nextIndex = startingIndex + 40
self.searchForSale(query: query, startingIndex: nextIndex)
}
}
})
}
}
}
}else{
return
}
}
SVProgressHUD.dismiss()
}.resume()
//hide keyboard
self.searchBar.endEditing(true)
}
In your completion handler if any results have been returned you end with:
DispatchQueue.main.async { self.tableView.reloadData() }
to trigger reloading of your table with the updated information. At this same point is where you could determine of there may be more results and initiate the next asynchronous URL task. In outline your code might be:
let needToContinueSearch : Bool = ...;
DispatchQueue.main.async { self.tableView.reloadData() }
if needToContinueSearch
{ // call routine it initiate next async URL task
}
(If there is any reason to start the task from the main thread the if would be in the block.)
By not initiating the next search until after you've processed the results of the first you avoid having to deal with any issues of a subsequent callback trying to update your data at the same time as a previous one.
However if you find delaying the second search in this way is too slow you can investigate ways to overlap the operations, e.g. you might have the callback just pass the processing of the results to an async task on a serial queue (so that only one set of results is being processed at once) and initiate the next async URL task.
HTH
Declare a bool variable as isLoading and if that function is loading dont trigger urlsession. hope below sample will help you.
var isLoading : Bool = false
func loadMore(with pageCount: Int){
if isLoading { return }
isLoading = true
// call the network
URLSession.shared.dataTask(with: URL(string: "xxxxx")!) { (data, response, error) in
// after updating the data set isloding to false again
// do the api logic here
//
DispatchQueue.main.async {
// self.items = downloadedItems
self.tableView.reloadData()
self.isLoading = false
}
}.resume()
}
I am working on an app that uses CoreData.
I am strong numbers and retrieving them, but when i store more than one field it only shows the last field with the number but a 0 in all the others. below is my codes.
to store them...
let CWConvert = Double(CWeight.text!)
storeTranscription18CW(pageText: (CWConvert)!, textFileUrlString: "cWeight")
savePlus += 1
let TWConvert = Double(TWeight.text!)
storeTranscription18TW(pageText: (TWConvert)!, textFileUrlString: "tWeight")
and...
func getContext () -> NSManagedObjectContext {
_ = UIApplication.shared.delegate as! AppDelegate
return DataController().managedObjectContext
}
func storeTranscription18CW (pageText: Double, textFileUrlString: String) {
let context = getContext()
//retrieve the entity that we just created
let entity = NSEntityDescription.entity(forEntityName: "TextInputs", in: context)
let transc = NSManagedObject(entity: entity!, insertInto: context)
// set the entity values
transc.setValue(pageText, forKey: "cWeight")
//save the object
do {
try context.save()
print("saved!")
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
} catch {
}
}
func storeTranscription18TW (pageText: Double, textFileUrlString: String) {
let contexta = getContext()
//retrieve the entity that we just created
let entitya = NSEntityDescription.entity(forEntityName: "TextInputs", in: contexta)
let transc = NSManagedObject(entity: entitya!, insertInto: contexta)
// set the entity values
transc.setValue(pageText, forKey: "tWeight")
//save the object
do {
try contexta.save()
print("saved!")
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
} catch {
}
}
and to retrive.
func getTranscriptions18CW () {
//create a fetch request, telling it about the entity
let fetchRequesta: NSFetchRequest<TextInputs> = TextInputs.fetchRequest()
do {
//go get the results
let searchResults18CW = try getContext().fetch(fetchRequesta)
for transa in searchResults18CW as [NSManagedObject] {
if let resulta = transa.value(forKey: "cWeight") {
if let stra = resulta as? String {
CWeight.text = stra
}else {
CWeight?.text = "\(resulta)"
}
}
}
//get the Key Value pairs (although there may be a better
}catch {
print("Error with request: \(error)")
}
}
func getTranscriptions18TW () {
//create a fetch request, telling it about the entity
let fetchRequest: NSFetchRequest<TextInputs> = TextInputs.fetchRequest()
do {
//go get the results
let searchResults18TW = try getContext().fetch(fetchRequest)
for trans in searchResults18TW as [NSManagedObject] {
if let result = trans.value(forKey: "tWeight") {
if let str = result as? String {
TWeight.text = str
}else {
TWeight?.text = "\(result)"
}
}
//get the Key Value pairs (although there may be a better way to do that...
}
}catch {
print("Error with request: \(error)")
}
}
i have tried different names but get the same it only shows the last one as the real number if i moment out the last one then the first shows the real value.
Try something more like this to save so that you are saving both in the same row.
func storeTranscription18TW () {
let contexta = getContext()
//retrieve the entity that we just created
let entitya = NSEntityDescription.entity(forEntityName: "TextInputs", in: contexta)
let transc = NSManagedObject(entity: entitya!, insertInto: contexta)
// set the entity values
transc.setValue(CWConvert, forKey: "cWeight") // Note the change from pageText
transc.setValue(TWConvert, forKey: "tWeight") // Note the change from pageText
//save the object
do {
try contexta.save()
print("saved!")
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
} catch {
}
}
Then when you do a get they would both be done in the same function as well.
I've been trying to delete an NSManagedObject.
This is my code:
let app = UIApplication.shared.delegate as! AppDelegate
let context = app.persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "MyEnt")
request.predicate = NSPredicate(format: "SELF = %#", EnttoDelete.objectID)
request.returnsObjectsAsFaults = false
do {
let results = try context.fetch(request)
if results.count > 0 {
for result in results as! [NSManagedObject] {
print ("Ent found")
context.delete(result)
do {
try context.save()
} catch {
print("failed to delete")
}
}
}
} catch {
print ("Error in do")
}
}
Has you see I have de Entitie do be deleted (EnttoDelete) and therefor it's ID (EnttoDelete.objectID).
Now I've researchedm even in stackoverflow and I think this should work. But it's not.
How can I delete desired entitie?
I think I sort this, doing a different thing:
let app = UIApplication.shared.delegate as! AppDelegate
let context = app.persistentContainer.viewContext
var thisID: NSManagedObjectID = (thatLand?.objectID)!
let object = context.object(with: thisID)
context.delete(object)
do {
try context.save()
} catch {
print("failed to delete")
}
I thinks it's the better solution. Not sure though!
Hello I am currently following a Swift tutorial which uses the old version of Swift and I am not able to follow this as I believe the syntax has changed in the newer version of Swift.
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
var appDel:AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
var context:NSManagedObjectContext = appDel.managedObjectContext
var newUser = NSEntityDescription.insertNewObjectForEntityForName("users", inManagedObjectContext: context) as NSManagedObject
newUser.setValue("Joe", forKey: "username")
newUser.setValue("pass", forKey: "password")
do {
try context.save()
} catch let error {
print("Couldn't save user data")
print(error)
}
let request = NSFetchRequest(entityName: "Users")
request.returnsObjectsAsFaults = false
// var results = context.executeFetchRequest(request)
do {
var results =
try context.executeFetchRequest(request)
results = results as! [NSManagedObject]
} catch let error as NSError {
print(error)
}
for result: AnyObject in results {
print(results)
}
}
The error I am receiving is to do with the results on the line for result: AnyObject in results and the error is unresolved identifier 'results' which is giving me the impression that this should be declared somewhere as a variable as it is currently unresolved but I cannot figure out how to fix this, any help would be greatly appreciated, thanks!
do {
var results = try context.executeFetchRequest(request)
results = results as! [NSManagedObject]
} catch let error as NSError {
print(error)
}
for result: AnyObject in results {
print(results)
}
results only has scope inside the do block there. You need to move the processing of the array inside the do:
do {
var results = try context.executeFetchRequest(request)
results = results as! [NSManagedObject]
for result in results {
print(results)
}
} catch let error as NSError {
print(error)
}
Also there's no need to lose information by casting as AnyObject.
With the new API's against CoreData (in Swift 3.0) you should do:
let request = NSFetchRequest<Users>(entityName: "Users")
request.returnsObjectsAsFaults = false
do {
var results =
try context.fetch(request)
// `results` will here be [Users]
} catch let error as NSError {
print(error)
}
The new signature of fetch is fetch<T : NSFetchRequestResult>(_ request: NSFetchRequest<T>) throws -> [T] where T is the same as provided in <HERE> (ex. NSFetchRequest<Users>)
Within my user object I added a column to add a users favorite team. The column is identified as favTeam and is a pointer to a teams class
Here is my code. I have populated my user with a favorite team however the logic is always showing that "favteam nil"
if let object = PFUser.currentUser()!["favTeam"] as? [PFObject]{
print("favteam not nil")
print(object)
let favTeam = PFUser.currentUser()!["favTeam"]
favTeamText.text = favTeam["Name"] as? String
if let favTeamImageView = favTeam["teamLogo"] as? PFFile {
favTeamImageView.getDataInBackgroundWithBlock { (imageData: NSData?, error: NSError?) -> Void in
if error == nil {
if let imageData = imageData {
self.teamLogo.image = UIImage(data: imageData)
}
}
}
}
}
else {
print("favteam nil")
}
I can accomplish this by using a PFUser.query() as follows...
func fetchFavoriteTeam() {
let userQuery: PFQuery = PFUser.query()!
userQuery.whereKey("username", equalTo: (currentUser?.username)!)
userQuery.findObjectsInBackgroundWithBlock({
(users, error) -> Void in
var favTeam = users!
if error == nil {
if favTeam != nil {
favTeamContainer = favTeam.valueForKey("favTeam") as! PFObject
}
} else {
print(error)
}
})
}