So I am creating a fairly simple program using Realm as my database. I am fairly new to programing in Swift (or any OS X or iOS environment.) In my program when a button is pressed IBAction func createInvoice I want a few things to happen, I want to count the previous rows in the database and create an invoice number, I want to write new data to the database and I want to call a new view and view controller and pass along the invoice number. My code works except for one thing when using Realm the new view controller is called (override func prepareForSegue) before the invoice number is created so a 0 value is passed along to the new view controller.
If I create a dummy invoice number value such as let invoicenumber = 42 everything works perfectly. It seems that Realm is causing things to happen 'out of order' How can I make the veiwcontroller wait for a value before loading?
#IBAction func createInvoice(sender: AnyObject) {
let realm = Realm()
let invoicepull = Invoice()
let invoicecount = realm.objects(Invoice)
let invoicenraw = invoicecount.count
let a = 100
let invoicenumber = a + invoicenraw
var invoicefile = Invoice()
invoicefile.inumber = invoicenumber
invoicefile.cnumber = clientcombo.stringValue
invoicefile.cost = owed.doubleValue
invoicefile.paid = paid.doubleValue
invoicefile.sevicecode = service.stringValue
invoicefile.dateofservice = NSDate()
// Save your object
realm.beginWrite()
realm.add(invoicefile)
realm.commitWrite()
//Sent notification
performSegueWithIdentifier("cinvoiceseuge", sender: nil)
println("Inside Action")
println(invoicenumber)
dismissViewController(self)
}
override func prepareForSegue(segue: NSStoryboardSegue, sender: AnyObject!) {
if (segue.identifier == "cinvoiceseuge") {
//Checking identifier is crucial as there might be multiple
// segues attached to same view
var detailVC = segue.destinationController as! invociegenerator;
detailVC.toPass = invoicenumber
println("Inside Sugue")
println(invoicenumber)
}
}
If createInvoice is happening on a different thread than prepareForSegue, you'll have to refresh the realm (Realm().refresh()) before accessing your invoicenumber variable (which I assume is of type RealmSwift.Object).
I have solved this issue, thanks to the help of #Shmidt by using Realm's built in notification center. To use the notifications you can use this basic structure.
var notificationToken: NotificationToken?
deinit{
let realm = Realm()
if let notificationToken = notificationToken{
realm.removeNotification(notificationToken)
}
}
override func viewDidLoad() {
super.viewDidLoad()
let realm = Realm()
notificationToken = realm.addNotificationBlock { note, realm in
println("The realm is complete")
}
...
}
One small other error in my code was let invoicenumber = a + invoicenraw I needed to drop the let as it is a variable and not a constant.
Related
Sorry about the title, i’m not quite sure how to stay this succinctly. In any case, in my (iOS/Swift but not SwfitUI) app, the user can edit an object (for example Team) over a number of screens. When I first start, I create a team using
// Team is subclass of Realm Object
let team = Team()
let realm = try Realm()
// save copy of team into a property or something in memory
realm.beginWrite()
realm.add(team)
}
and then later in the app, after a number of interactions with the user:
var team = // fetch copy of team from memory
let realm = try Realm()
team.name="bar"
// other updates to "team".
try realm.commitWrite()
This seems to work fine, however I was just wondering if this is “OK” to do since I’m calling beginWrite and commitWrite in different calls to let realm = Realm().
I’m sure that the user has not and will not perform any other realm queries/writes during this flow since if the user “cancels” out of editing the “team”, I call realm.cancelWrite.
Lastly, does the answer change when using a synced realm vs. a local realm?
Thanks!
A more complete (yet still simplified) example of what I’m doing looks like this:
class MyViewController: UIViewController {
private var team: Team?
#IBOutlet weak var nameTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
do {
// setup realm configuration up here somewhere
let realm = try Realm()
realm.beginWrite()
let team = Team()
realm.add(team)
} catch {
print("Error: \(error)")
}
}
#objc func submitTapped(_ sender: Any) {
let name = self.nameTextField.text!.trim()
guard let team = self.team else {
return
}
do {
let realm = try Realm()
self.team.name = name
try realm.commitWrite()
} catch {
print ("Error: \(error)")
}
}
}
I keep getting a fatal error saying how a value was unwrapped and it was nil and I don't understand how. When I instantiate a view controller with specific variables they all show up, but when I perform a segue to the exact VC, the values don't show up.
Take these functions for example...
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
tableView.deselectRow(at: indexPath, animated: true)
if let displayVC = storyboard?.instantiateViewController(withIdentifier: Constants.Storyboards.TeachStoryboardID) as? SchoolEventDetailsViewController {
displayVC.selectedEventName = events[indexPath.row].eventName
displayVC.selectedEventDate = documentsDate[indexPath.row].eventDate
displayVC.selectedEventCost = documentsCost[indexPath.row].eventCost
displayVC.selectedEventGrade = documentsGrade[indexPath.row].eventGrade
displayVC.selectedEventDocID = documentsID[indexPath.row]?.docID
navigationController?.pushViewController(displayVC, animated: true)
}
}
This combined with this function :
func verifyInstantiation() {
if let dateToLoad = selectedEventDate {
dateEditableTextF.text = dateToLoad
}
if let costToLoad = selectedEventCost {
costEditableTextF.text = costToLoad
}
if let gradesToLoad = selectedEventGrade {
gradesEditableTextF.text = gradesToLoad
}
if let docIDtoLoad = selectedEventDocID {
docIDUneditableTextF.text = docIDtoLoad
}
if let eventNameToLoad = selectedEventName {
eventNameEditableTextF.text = eventNameToLoad
}
}
Helps load the data perfectly, but when I try to perform a segue from a search controller the data is not there.
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.title = selectedEventName
I set the title of the vc to have the event name , and I also recently added a text field to store it as well for experimental purposes (this question).
Now the issue is I want to do a data transfer from an Algolia Search Controller to that VC and I got all the other fields to show up, except for one and that was the document ID. So I created a completion handler function to get the document ID as a string and have it inserted into the vc when the segue is performed, just like how it's there when the vc is instantiated.
Here is the function :
func getTheEventDocID(completion: #escaping ((String?) -> ())) {
documentListener = db.collection(Constants.Firebase.schoolCollectionName).whereField("event_name", isEqualTo: selectedEventName ?? navigationItem.title).addSnapshotListener(includeMetadataChanges: true) { (querySnapshot, error) in
if let error = error {
print("There was an error fetching the documents: \(error)")
} else {
self.documentsID = querySnapshot!.documents.map { document in
return EventDocID(docID: (document.documentID) as! String)
}
let fixedID = "\(self.documentsID)"
let substrings = fixedID.dropFirst(22).dropLast(3)
let realString = String(substrings)
completion(realString)
}
}
}
I thought either selectedEventName or navigationItem.title would get the job done and provide the value when I used the function in the data transfer function which I will show now :
//MARK: - Data Transfer From Algolia Search to School Event Details
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
otherVC.getTheEventDocID { (eventdocid) in
if let id = eventdocid {
if segue.identifier == Constants.Segues.fromSearchToSchoolEventDetails {
let vc = segue.destination as! SchoolEventDetailsViewController
vc.selectedEventName = self.nameTheEvent
vc.selectedEventDate = self.dateTheEvent
vc.selectedEventCost = self.costTheEvent
vc.selectedEventGrade = self.gradeTheEvent
vc.selectedEventDocID = id
}
}
}
}
But it ends up showing nothing when a search result is clicked which is pretty upsetting, I can't understand why they're both empty values when I declared them in the SchoolEventDetailsVC. I tried to force unwrap selectedEventName and it crashes saying there's a nil value and I can't figure out why. There's actually a lot more to the question but I just tried to keep it short so people will actually attempt to read it and help since nobody ever reads the questions I post, so yeah thanks in advance.
I'm a litte confused what the otherVC is, which sets a property of itself in the getTheEventDocID, whilste in the closure you set the properties of self, which is a different controller. But never mind, I hope you know what you are doing.
Since getTheEventDocID runs asynchronously, the view will be loaded and displayed before the data is available. Therefore, viewDidLoad does not see the actual data, but something that soon will be outdated.
So, you need to inform the details view controller that new data is available, and refresh it's user interface. Something like
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
otherVC.getTheEventDocID { (eventdocid) in
if let id = eventdocid {
if segue.identifier == Constants.Segues.fromSearchToSchoolEventDetails {
let vc = segue.destination as! SchoolEventDetailsViewController
vc.selectedEventName = self.nameTheEvent
vc.selectedEventDate = self.dateTheEvent
vc.selectedEventCost = self.costTheEvent
vc.selectedEventGrade = self.gradeTheEvent
vc.selectedEventDocID = id
vc.updateUI()
}
}
}
}
and in the destination view controller:
class SchoolEventDetailsViewController ... {
override func viewDidLoad() {
super.viewDidLoad()
updateUI()
}
func updateUI () {
navigationItem.title = selectedEventName
// and so on
}
}
Ok so I decided to attempt a workaround and completely ditched the getTheEventDocID() method because it was just causing me stress. So I decided to ditch Firebase generated document IDS and just use 10 digit generated ids from a function I made. I also figured out how to add that exact same 10 digit id in the Algolia record by just storing the random 10 digit id in a variable and using it in both places. So now instead of using a query call to grab a Firebase generated document ID and have my app crash everytime I click a search result, I basically edited the Struct of the Algolia record and just added an eventDocID property that can be used with hits.hitSource(at: indexPath.row).eventDocID.
And now the same way I added the other fields to the vc by segue data transfer, I can now do the same thing with my document ID because everything is matching :).
This is my first attempt at XCode, used to work on MatLab so very new to this. I have a VC here (named guests2ViewController) which I'm trying to send data to the next VC (named resultsViewController). Unfortunately the VC is exporting the data from the lines (print "b") instead of the earlier lines (print "a"). Why is this, and how could I fix it?
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let vc = segue.destination as? resultsViewController
if segue.identifier == "toresults"{
//prioritise this part of code - call it part A
Database.database().reference(withPath: self.password).observeSingleEvent(of: .value, with: { snapshot in
//dates
var arr = [String]()
//times
var arr1 = [String]()
//number of attendees
var arr2 = [String]()
let enumerator = snapshot.children
while let rest = enumerator.nextObject() as? DataSnapshot {
let newobj=rest.children
while let rest1 = newobj.nextObject() as? DataSnapshot {
arr.append(rest.key)
arr1.append(rest1.key)
arr2.append(String(rest1.childrenCount))
let guests = arr2.max()
var index = 0
for n in arr2 {
if n == guests {
//print (index)
let datefromarray = String(arr[index])
let timefromarray = String(arr1[index])
let guests1 = String(Int(guests!)!)
vc?.databasedate = (datefromarray)
vc?.databasetime = (timefromarray)
vc?.databaseguests = (guests1)
break
}
index += 1
}
}
}
print(vc?.databasedate)
print(vc?.databasetime)
print(vc?.databaseguests)
print("a")
//this doesn't get sent to the next VC after taking the data from Firebase
})
}
print(vc?.databasedate)
print(vc?.databasetime)
print(vc?.databaseguests)
print("b")
//this gets sent to the next VC
}
}
Data is loaded from Firebase (and most modern web APIs) asynchronously. This is to prevent blocking the user from using your app, while the (possibly slow) network request is in progress.
If you check in a debugger, you'll see that print("b") happens before vc?.databasedate = (datefromarray), which explains why you're passing the wrong value to the next view controller.
The solution is always the same: any code that needs data from the database needs to be inside the callback/closure/completion handler, or be called from there.
For more on this and code examples, see:
Firebase with Swift 3 counting the number of children
Why isn't my function that pulls information from the database working?
Access Firebase variable outside Closure
getting data out of a closure that retrieves data from firebase
Swift / How to use dispatch_group with multiple called web service?
Completion handler Firebase observer in Swift
In my program when a button is pressed I am adding information to a database, including creating invoice number then calling a segue to a new view controller. When the new view controller is called I'd like to pass along that invoice number. Everything works fine, I can pass along sample data no problem. However, it appears that "override func prepareForSegue(segue: NSStoryboardSegue, sender: AnyObject!) {}" is being called before my button (upon initialization of the view controller?), so I am passing along a blank value. How can I make my prepareForSegue wait till after my button is pressed? Here is the code I currently have.
#IBAction func createInvoice(sender: AnyObject) {
let realm = Realm()
let invoicepull = Invoice()
let invoicecount = realm.objects(Invoice)
let invoicenraw = invoicecount.count
let a = 100
let invoicenumber = a + invoicenraw
var invoicefile = Invoice()
invoicefile.inumber = invoicenumber
invoicefile.cnumber = clientcombo.stringValue
invoicefile.cost = owed.doubleValue
invoicefile.paid = paid.doubleValue
invoicefile.sevicecode = service.stringValue
invoicefile.dateofservice = NSDate()
// Save your object
realm.beginWrite()
realm.add(invoicefile)
realm.commitWrite()
//Sent notification
performSegueWithIdentifier("cinvoiceseuge", sender: nil)
println("Inside Action")
println(invoicenumber)
dismissViewController(self)
}
override func prepareForSegue(segue: NSStoryboardSegue, sender: AnyObject!) {
if (segue.identifier == "cinvoiceseuge") {
//Checking identifier is crucial as there might be multiple
// segues attached to same view
var detailVC = segue.destinationController as! invociegenerator;
detailVC.toPass = invoicenumber
println("Inside Sugue")
println(invoicenumber)
}
}
Update: I belive this is an issue with the Realm database causing it to behave unexpectedly. If I remove all realm code, the program works as expected and I can pass a static dummy value.
invoicenumber in createInvoice() is a local variable and invoicenumber in prepareForSegue() seems to be an instance variable. is it what you expected?
I have a CoreData entity named 'Studio' with an attribute named 'name' with an NSManagedObject subclass created.
My app designed for a simple process, enter a name into a text box, and press 'save' and the name is saved into Studio.name - Press 'Update' and a text label is refreshed to show the value of Studio.name
However, it is not functioning as expected, if I, for example, enter the name 'Stack' and save the update I see 'Stack' in the text label, if i then enter 'Overflow' save/update the label reads 'Overflow', If i update it a third time to 'Swift' save/update the label again reads 'Stack'.
From there updates will give one of the three values seemingly at random.
Force quitting the app and relaunching it shows that the data is being saved to Core Data as pressing the update button will return a random previous value.
My question is, how does this happen with a string? (Shouldn't it only hold one value at a time?)
How can I correct this so it will only hold a single value and any subsequent values simply overwrite the previous value?
My code follows.
import UIKit
import CoreData
class ViewController: UIViewController {
#IBOutlet weak var studioBox: UITextField!
#IBOutlet weak var nameLabel: UILabel!
#IBAction func saveData(sender: AnyObject) {
var studio = writeStudioData()
studio.name = studioBox.text
}
#IBAction func Update(sender: AnyObject) {
var studio = getStudioData()
nameLabel.text = studio.name
}
func getStudioData() -> Studio {
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
let managedContext = appDelegate.managedObjectContext!
let request = NSFetchRequest(entityName: "Studio")
request.returnsObjectsAsFaults = false
let result = managedContext.executeFetchRequest(request, error: nil) as [Studio]
return result[0]
}
func writeStudioData () -> Studio {
let appDelegate =
UIApplication.sharedApplication().delegate as AppDelegate
let managedContext = appDelegate.managedObjectContext!
let entityDescription = NSEntityDescription.entityForName("Studio", inManagedObjectContext: managedContext)
let result = Studio(entity: entityDescription!, insertIntoManagedObjectContext: managedContext)
return result
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
You don't have one object, you are creating a new object every time. As you aren't including a sort descriptor with your fetch request, the order you get them, and thus the corresponding name, is unspecified, meaning it could be any of them.
You could either perform a fetch first in writeStudioData to see if there's already an object, only creating one if there isn't, or you could create one object and keep it around in a property.