Core data does not save the data properly - swift

Question

EDITED
I have a UITableView which displays multiple social media posts. I use the Prefetch Source Delegate for prefetching Posts and I use Core Data to be stored after being fetched from web server. Problem that I have is that I get no error, but the data does not stay saved between launches in CoreData.
Snip of code
func configureDataSourceTable(){
self.dataSource = UITableViewDiffableDataSource<String,String>(tableView: self.table_view){
(tableView, indexPath, ref) -> UITableViewCell? in
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! CheckInCell
if !self.postData.currentPostFetching(ref: ref){
self.postData.fetchPost(ref: ref) { post in
DispatchQueue.main.async {
self.setPostNeedsUpdate(ref: ref)//reconfigure items
}
return cell
}
func fetchPost(ref: String,completion : (PostStruct)->Void) {
if self.dataContainer.postIsPartOfCoreData(ref: ref){
var postStruct = self.dataContainer.getPostStructFromDB(ref: ref)
completion(postStruct)
}else{ //has to be downloaded from web server
Task {
let post = await getPostFromServer()//not relevant in understanding problem
var postStruct = self.convertDataToPost(post)
completion(postStruct)
self.dataContainer.savePostStruct(post: postStruct)
}
}
}
Class of the DataContainer subclass of NsPersistentStore
func savePostStruct(post_struct : PostStruct,image_data : String){
Task.detached {
var postObject = PostCore.init(context : self.viewContext)
postObject.name = "Test"
var image = ImageCore.init(context: self.viewContext)
imageObject.data = image_data
postObject.image = imageObject
do {
if Thread.isMainThread {
print("Running on the main thread parent")
}else {
print("Other thread")
}
try self.viewContext.save()
print("Reference \(post_struct.ref) child saved")
}catch {
print("Error that produced \(post.ref) catched while trying to savethe data on child: \(error.localizedDescription),number : \(error)");
}
if post_struct.ref == "AAAA"{
var post = PostCore.fetchRequest()
var predicate = NSPredicate.init(format: "ref like %#", post.ref!)
fetchCheckIn.predicate = predicate
fetchCheckIn.fetchLimit = 1
fetchCheckIn.includesPropertyValues = true
let result = try! self.viewContext.fetch(fetchCheckIn)
print(result)
//This line returns the Object
print(self. checkPostExistHasPictures(refPost: post.ref))
//This is the line where always come (false, false) meaning that the Post is not saved
}
}
func getPostStructFromDB(refPost : String)async->PostStruct {
return await self.viewContext.perform{
var fetchPost = PostCore.fetchRequest()
var predicate = NSPredicate.init(format: "ref like %#", refPost)
fetchPost.predicate = predicate
fetchPost.fetchLimit = 1
fetchPost.includesSubentities = true
fetchPost.returnsObjectsAsFaults = false
fetchPost.includesPropertyValues = true
let result = try? self.viewContext.fetch(fetchCheckIn)
var refPost = result.first.ref
return PostStruct(ref : ref, image: refPost.image.data)
}
}
}
func checkPostExistHasPictures(refPost : String)->(Bool,Bool){
var fetchCheckIn = CheckInCore.fetchRequest()
var predicate = NSPredicate.init(format: "ref like %#", refPost)
fetchCheckIn.predicate = predicate
fetchCheckIn.fetchLimit = 1
var exist = false
var hasPicture = false
self.viewContext.performAndWait {
do{
let result = try? self.viewContext.fetch(fetchCheckIn)
if result?.first == nil {
}else {
print("Exists with reference \(reference_checkin)")
if result!.first!.pic_ref == nil {
exist = true
hasPicture = false
}else if result!.first!.image!.count != 0 {
exist = true
hasPicture = true
}
}
}catch {
print("error catched")
}
}
return(exist, hasPicture)
}
}
Relation between PostCore and ImageCore is zero to many.
I don't get any error code or error message. I commented the line where I get the error. I have tried all possible ways using a backGroundContext each time a save is made to not block the main thread and still is the same problem.

Answer 1

Your code is extremely confusing.
Why have you got Task scattered everywhere, you are doing no async/await work?
Your savePostStruct method takes a parameter called post which contains your data, then you immediately replace it with a value of the same name of type PostCore, which is presumably a managed object, then you only set one value on it.
Then, when you come to fetch an item, there's nothing there, because you haven't written anything to the managed object besides the name "Test".
At the very least, you have to change this line:
var post = PostCore.init(context : self.viewContext)
To
let postObject = PostCore(context: self.viewContext)
Then you won't get confused between the managed object and the struct you're passing in.
You are also saving the context before you've written any of the values to it.