User-entered data not being saved or appearing in tableview - ios

Question

I'm having issues trying to append a core data entity called products - I used the same code that I used to add companies, which works fine. The only difference in the app is that there is just one "static" tableview of companies I guess you could say, whereas the tableview for products is dynamically set depending on which company cell is tapped. But I'm not sure how that would cause the problem.
I've been debugging/checking values all over the app since yesterday and it seems like no matter what I try to alter, products.count in numberOfRowsInSection remains 0.
I call a function called handleSave() when the user hits a done button after entering new values in three text fields, just like with my other object companies:
func handleSave() {
guard let newProductUrl = NSURL(string: urlTextField.text!) else {
print("error getting text from product url field")
return
}
guard let newProductName = self.nameTextField.text else {
print("error getting text from product name field")
return
}
guard let newProductImage = self.logoTextField.text else {
print("error getting text from product logo field")
return
}
self.productController?.save(name: newProductName, url: newProductUrl as URL, image: newProductImage)
let cc = UINavigationController()
let companyController = CompanyController()
viewController = companyController
cc.viewControllers = [companyController]
present(cc, animated: true, completion: nil)
}
This then calls the save function to append products:
func save(name: String, url: URL, image: String) {
guard let appDelegate =
UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext =
appDelegate.persistentContainer.viewContext
let entity =
NSEntityDescription.entity(forEntityName: "Product",
in: managedContext)!
let product = NSManagedObject(entity: entity,
insertInto: managedContext)
product.setValue(name, forKey: "name")
product.setValue(url, forKey: "url")
product.setValue(image, forKey: "image")
do {
try managedContext.save()
products.append(product)
} catch let error as NSError {
print("Could not save. \(error), \(error.userInfo)")
}
tableView.reloadData()
}
And the data is fetched in viewWillAppear
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
guard let appDelegate =
UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext =
appDelegate.persistentContainer.viewContext
let companyToDisplay = self.navigationItem.title!
let fetchRequest =
NSFetchRequest<NSManagedObject>(entityName: "Product")
fetchRequest.predicate = NSPredicate(format:"company.name == %#",companyToDisplay)
do {
products = try managedContext.fetch(fetchRequest)
print(products)
} catch let error as NSError {
print("Could not fetch. \(error), \(error.userInfo)")
}
}
When this exact same process is used for adding companies, the new company then appears in the tableview. However now with products, that is not the case; the tableview remains empty. I'm not sure what the difference is and I'm not experienced enough with core data that I feel like I can figure out where the problem lies.
Huge thanks in advance to anyone that can figure this out!

Answer 1

After invoking handleSave() & before performing table.reloadData(), you need to perform db fetch operations done in viewWillAppear().
Segregate your fetchRequest logic out of viewWillAppear() into a function called (say) fetchUpdatedData().
Now, after try managedContext.save(), do a fetchUpdatedData(), update your product data arrays & then update the UI by table.reloadData()

Answer 2

Use a NSFetchedResultsController to keep your view in sync with your model. NSFetchedResultsController monitors core-data and sends a delegate message when there are updates - then you can update your tableview. Otherwise you have to manually do a refresh whenever core-data changes.