Core Data Object was written to, but never read - swift

As I try to update an existing entry in my Core Data DB, I fetch the desired item by id, change it to a new item and save in context.
However, when I fetch the object and replace it, I get the warning "Core Data Object was written to, but never read." It does make sense since I'm not really using that object, but as I understand it, just giving it a value saves it in Core Data.
static var current: User? {
didSet {
if var userInCoreData = User.get(with: current?.id), let current = current { //userInCoreData is the value with the warning
userInCoreData = current
}
CoreDataManager.saveInContext()
}
}
static func get(with id: String?) -> User? {
guard let id = id else { return nil }
let request: NSFetchRequest = User.fetchRequest()
let predicate = NSPredicate(format: "id = %#", id)
request.predicate = predicate
do {
let users = try CoreDataManager.managedContext.fetch(request)
return users.first
} catch let error {
print(error.localizedDescription)
return nil
}
}
I want to make sure, is this the recommended process to overwrite a value in Core Data, or am I doing something wrong?

This section
if var userInCoreData = User.get(with: current?.id), let current = current { //userInCoreData is the value with the warning
userInCoreData = current
}
seems just updating local variable userInCoreData, not User object in Core Data.
So the warning says "you fetched data from core data and set to a variable, but you set another value to the variable soon, never use the first value from core data. Is it OK?"
What you really want to do is something like this?
if var userInCoreData = User.get(with: current?.id), let current = current {
userInCoreData.someValue = current.someValue
userInCoreData.anotherValue = current.anotherValue
}

Related

Firebase's ref().child(stringPath: String) returning the entire top level collection

I'm trying to retrieve a specific child of my Firebase database using swiftUI. To do that I use the simple expression
func addListeners() {
let database = Database.database(url: "https://someUrl")
let ref = database.reference(withPath: "users")
let currentUserId = "u3Ebr6M3BAbP7PBSYYJ7q9kEe1l2"
let drivingTowardsRef = database.reference(withPath: "users/\(currentUserId)/drivingTowardsUsers")
print("Loading data from \(drivingTowardsRef)")
//THIS RIGHT HERE IS CAUSING THE PROBLEM
ref.observe(.childAdded) { snapshot in
print("Got TOP LEVEL data for user \(snapshot.key): \(String(describing: snapshot.value))")
}
//---------------------------------------
drivingTowardsRef.observe(.childAdded) { snapshot in
ref.child(snapshot.key).getData { (error, userSnapshot) in
if let error = error {
print(error)
} else {
print("Got arriving user data \(snapshot.key): \(String(describing: userSnapshot.value))")
}
}
}
}
The function will just return the entire database data
EDIT: The function returns the data from the first observer ref top level in this case users/ which in my case has two elements: niixi6iORjNn8gWq6tKvSi3Bxfc2, u3Ebr6M3BAbP7PBSYYJ7q9kEe1l2
Got arriving user data niixi6iORjNn8gWq6tKvSi3Bxfc2: Optional({
niixi6iORjNn8gWq6tKvSi3Bxfc2 = {
aproxTime = 0;
distance = 0;
latitude = "37.33070704";
longitude = "-122.03039943";
parkingMode = searching;
userId = niixi6iORjNn8gWq6tKvSi3Bxfc2;
username = testeroNumero;
};
u3Ebr6M3BAbP7PBSYYJ7q9kEe1l2 = {
aproxTime = 0;
distance = 0;
drivingTowardsUsers = {
niixi6iORjNn8gWq6tKvSi3Bxfc2 = {
approxTime = 0;
distance = "560.1447571016249";
};
};
latitude = "37.32984184";
longitude = "-122.02018095";
parkingMode = offering;
userId = u3Ebr6M3BAbP7PBSYYJ7q9kEe1l2;
username = cleoBadu;
};
The key for the child path I pass him seems to be correct but it's still returning the entire top level collection instead of the single item...
EDIT: The problem seems to be on the first observer which messes up the .getData() of the ref.child(snapshot.key). Is that even possible?
Just commenting out that ref.observe(.childAdded) will automatically make the second ref.child(snapshot.key) behave totally normally
What am I missing?
I could get the entire database as a single mega dictionary and then get the child I want from there but it doesn't seem really conventional, especially when google's library offers the possibility to not do that.
EDIT: I added a printing statement that prints the url of the database ref. If I then type in the url on my browser, it redirects me on the FRT database and landing me on the correct object. So the url it's generating is correct and works perfectly fine.
Still the object returned by the getData() is the entire db
SN: I removed all codable structs as that is not the problem, so the question is more focused on the actual problem
EDIT: Created a simple view as that. On a clean project it works on my project it doesn't. I guess it's some sort of configuration but's it's hard to look into it.
PROBLEM: Whatever child(string) I pass him it returns the entire top level data either way (replacing so snapshot.key). For example: I pass the key "something" -> all users are returned, I pass the key "" all users are returned
I just tried to reproduce the problem with (mostly) your code and data, but am not getting the same behavior.
I put the equivalent data into a database of mine at: https://stackoverflow.firebaseio.com/68956236.json?print=pretty
And used this code in Xcode 1.2 with Firebase SDK version 8.6.1:
let ref: DatabaseReference = Database.database().reference().child("68956236")
let currentUserId: String = "u3Ebr6M3BAbP7PBSYYJ7q9kEe1l2"
let drivingTowardsRef: DatabaseReference! = ref.child("\(currentUserId)/drivingTowardsUsers");
print("Loading data from \(drivingTowardsRef)")
drivingTowardsRef.observe(.childAdded) { snapshot in
ref.child(snapshot.key).getData { (error, userSnapshot) in
if let error = error {
print(error)
} else {
do {
//let parkingUser = try userSnapshot.data(as: ParkingUser.self)
print("Got data for user \(snapshot.key): \(String(describing: userSnapshot.value))")
} catch {
print("There has been an error while decoding the user location data with uid \(snapshot.key), the object to be decoded was \(userSnapshot). The decode failed with error: \(error)")
}
}
}
}
The output I get is:
Loading data from Optional(https://stackoverflow.firebaseio.com/68956236/u3Ebr6M3BAbP7PBSYYJ7q9kEe1l2/drivingTowardsUsers)
2021-08-27 10:39:09.578043-0700 Firebase10[36407:3458780] [] nw_protocol_get_quic_image_block_invoke dlopen libquic failed
Got data for user niixi6iORjNn8gWq6tKvSi3Bxfc2: Optional({
aproxTime = 0;
distance = 0;
latitude = "37.32798355";
longitude = "-122.01982712";
parkingMode = searching;
userId = niixi6iORjNn8gWq6tKvSi3Bxfc2;
username = testeroNumero;
})
As far as I can see this behavior is correct, but different from what you get. I hope knowing that I don't see the same behavior, and what versions I use, may be helpful to you.
This is not an issue with Firebase but rather client-side handling of the data returned, You’re expecting a Double within your Codable struct but supplying a String in the other end— Can you try:
public struct ParkingUser: Codable {
var latitude: String
var longitude: String
}

How do I build a custom object that consists of 2 custom objects for an expanding cell?

I am following along this tutorial here for collapsing UITableViewCells and the mechanics are quite straight forward but I am not quite sure how to populate my model arrays from Firestore. He has manually created the data for demo purposes so naturally as a beginner, I am stumbling since instead of that I am making a network call to Firebase.
My data structure is simple. The base collection (which would populate the title of the cell) extracts data from here: db.collection("Insurance_Plans") and contains the following strings:
- Holder name
- Holder contact etc.
And each insurance holder has multiple properties insured and this is the sub-collection i.e. db.collection("Insurance_Plans").document(planId).("Insured_Property") and data model consists of strings such as:
- Property type
- Property address etc.
What I am doing is creating the main struct:
struct cellData {
var opened = Bool()
var plans = [Plan]()
var properties = [Properties]()
}
and in the class itself I declare an instance of it it as:
var tableViewData = [cellData]()
Then I query the insurance meta data (which has its own function) as follows:
db.collection("Insurance_Plans").getDocuments() {
documents, error in
guard let snapshot = documents else {
let error = error
print("Error fetching documents results: \(error!.localizedDescription)")
return
}
let results = snapshot.documents.map { (document) -> Plan in
if let plan = Plan(dictionary: document.data(), id: document.documentID) {
self.plansArray.append(plan)
self.loadPropertyData(planId: document.documentID) // another function where property details are queried
return plan
} else {
fatalError("Unable to initialize type \(Plan.self) with dictionary \(document.data())")
}
}
self.plansArray = results
self.plansDocuments = snapshot.documents
self.plansTableView.reloadData()
}
Then I query the properties in each plan as such:
db.collection("Insurance_Plans").document(planId).collection("Properties").getDocuments() { documents, error in
guard let snapshot = documents else {
let error = error
print("Error fetching documents results: \(error!.localizedDescription)")
return
}
let results = snapshot.documents.map { (document) -> Property in
if let property = Property(dictionary: document.data()) {
return property
} else {
fatalError("Unable to initialize type \(Property.self) with dictionary \(document.data())")
}
}
self.propertiesArray = results
self.propertiesDocuments = snapshot.documents
self.ordersTableView.reloadData()
}
My question then is how do I enter the insurance meta data and the subsequent properties data into a cellData object and where do I do this?

Reset Core Data Bool for All Objects

I would like to set the bool value to false for every object in my core data entity.
This is how I am currently setting an individual value in core data:
func updateFriendSaidHi(friend: Friends, in context: NSManagedObjectContext = CoreDataStack.shared.container.newBackgroundContext()){
context.performAndWait {
// Update value to true in core data
friend.saidHi = true
saveToPersistentStore()
}
}
You could loop through each item in the entity but I'm guessing there's a better way to do this.
Any input would be great.
You could change the attributes of all records with Key-Value Coding
let request = NSFetchRequest<Friends> = Friends.fetchRequest()
context.performAndWait {
do {
let friends = context.fetch(request)
(friends as NSArray).setValue(true, forKey:"saidHi")
saveToPersistentStore()
} catch { print(error) }
}

Object has been deleted or invalidated realm

I have this class inherit from Object:
class Location: Object {
dynamic var id: String = ""
dynamic var name: String = ""
override class func primaryKey() -> String {
return "id"
}
}
This class is used as an instance inside my manager like this:
class LocationServiceAPI {
fileprivate var _location: Location?
var location: Location? {
get {
if _location == nil {
let realm = try! Realm()
_location = realm.objects(Location.self).first
}
return _location
}
set {
let realm = try! Realm()
if let newValue = newValue {
// delete previous locations
let locations = realm.objects(Location.self)
try! realm.write {
realm.delete(locations)
}
// store new location
try! realm.write {
realm.add(newValue, update: true)
_location = newValue
}
} else {
let locations = realm.objects(Location.self)
try! realm.write {
realm.delete(locations)
}
}
}
}
}
So whenever I get a location I delete the old one (new and old locations could be identical) and replace it with the new one, then I used the newValue as new value for the property _location but whenever I try to access the location it gives me 'Object has been deleted or invalidated'.
I am really confused since location will hold the value passed from the setter but not the realm!!
Note: If I stop the deleting then It will work fine.
The Object has been deleted or invalidated error will occur if an object has been deleted from a Realm, but you subsequently try and access a stored property of an instance of that object that your code was hanging onto since before the deletion.
You'll need to examine your logic paths and make sure there's no way you're deleting the location object, and not subsequently updating the _location property. There's no mention of deleting the object in the sample code you've provided, but your if let newValue = newValue line of code would mean that _location wouldn't actually get cleared if you passed in nil.
Finally, it's possible to manually check if an object has been deleted from a Realm by calling _location.invalidated, so if this happens a lot, it might be a good idea to include some extra checks in your code as well.
Without knowing really anything about your app and your design choices, it looks like you're trying to avoid reading/writing to the DB too often by caching the location property. Unless you're working with tons of LocationServiceAPI objects it shouldn't be a real performance penalty to actually read/write directly in the DB, like this :
class LocationServiceAPI {
var location: Location? {
get {
let realm = try! Realm()
return realm.objects(Location.self).first
}
set {
let realm = try! Realm()
if let newValue = newValue {
// store new location
try! realm.write {
realm.add(newValue, update: true)
}
} else {
// delete the record from Realm
...
}
}
}
}
Also, I would in general avoid keeping Realm objects along for longer periods, I don't say it's not possible but in general it leads to issues like you've experienced (especially if do multi-threading). In most cases I'd rather fetch the object from DB, use it, change it and save it back in the DB asap. If keeping references to specific records in the DB is necessary I'd rather keep the id and re-fetch it when I need it.

How do you store a dictionary on Parse using swift?

I am very new to swift and I don't know Obj C at all so many of the resources are hard to understand. Basically I'm trying to populate the dictionary with PFUsers from my query and then set PFUser["friends"] to this dictionary. Simply put I want a friends list in my PFUser class, where each friend is a PFUser and a string.
Thanks!
var user = PFUser()
var friendsPFUser:[PFUser] = []
var friendListDict: [PFUser:String] = Dictionary()
var query = PFUser.query()
query!.findObjectsInBackgroundWithBlock {
(users: [AnyObject]?, error: NSError?) -> Void in
if error == nil {
// The find succeeded.
println("Successfully retrieved \(users!.count) users.")
// Do something with the found objects
if let users = users as? [PFUser] {
friendsPFUser = users
for user in friendsPFUser{
friendListDict[user] = "confirmed"
}
user["friends"] = friendListDict //this line breaks things
user.saveInBackground()
}
} else {
// Log details of the failure
println("Error: \(error!) \(error!.userInfo!)")
}
}
To be clear, this code compiles but when I add
user["friends"] = friendListDict
my app crashes.
For those who might have this issues with. "NSInternalInconsistencyException" with reason "PFObject contains container item that isn't cached."
Adding Objects to a user (such as arrays or dictionaries) for security reasons on Parse, the user for such field that will be modified must be the current user.
Try signing up and using addObject inside the block and don't forget do save it!
It helped for a similar problem I had.