Check out example codes for "fetch request core data". It will help you in understanding the concepts better.

Code Example 1

// entire usable func for fetching data
    func loadData() {
        if let context = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer.viewContext {
            if let hellos = try? context.fetch(Hello.fetchRequest()) as? [Hello] {
                
            }
            
        }
    }

Code Example 2

override func viewWillAppear(_ animated: Bool) {
        if let context = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer.viewContext {
            if let coreDataToDoItems = try? context.fetch(ToDoItem.fetchRequest()) as? [ToDoItem] {
                toDo = coreDataToDoItems
            }
    }
}

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