Use core data index to fetch a specific item from core data

Question

My swift code below when loaded places 3 items in the core data entity named "UserName". When the user enters a number into textfield enterT I want the label labelName to display it. So when the user enters 1 the label should display jessica biel because Jesical Biel is the first name entered. Someone stated the suggestion below to solve this problem. I dont know exactly how to do this.I have added a gif below.

Convert the entered number to Int. If this succeeds pass the integer to joke and fetch the record matching the idx attribute.

https://github.com/redrock34/index-fetch

import UIKit import CoreData

  class ViewController: UIViewController,UITextFieldDelegate {
@IBOutlet var labelName : UILabel!
@IBOutlet var enterT : UITextField!

lazy var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

override func viewDidLoad() {
    super.viewDidLoad()

    openDatabse()
    fetchData()
    enterT.delegate = self


}

func textFieldDidEndEditing(_ textField: UITextField) {
    guard let index = Int(textField.text!) else {
        // display an alert about invalid text
        return
    }
    joke(at: index - 1)
}

func joke(at index : Int) {
    let fetchRequest = NSFetchRequest<Users>(entityName: "Users")
    fetchRequest.predicate = NSPredicate(format: "idx == %d", Int32(index))
    do {
        if let user = try context.fetch(fetchRequest).first {
            labelName.text = user.username
        }
    } catch {
        print("Could not fetch \(error) ")
    }
}
func openDatabse()
{
    let names = ["kim kardashian", "jessica biel", "Hailey Rienhart"]
    for i in 0..<names.count {
        let newUser = Users(context: context)
        newUser.username = names[i]
        newUser.idx = Int32(i + 1)
    }
    print("Storing Data..")
    do {
        try context.save()
    } catch {
        print("Storing data Failed", error)
    }
}
func fetchData()
{
    print("Fetching Data..")
    let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
    request.returnsObjectsAsFaults = false
    do {
        let result = try context.fetch(request)
        for data in result as! [NSManagedObject] {
            let userName = data.value(forKey: "username") as! String

            print("User Name is : "+userName)
        }
    } catch {
        print("Fetching data Failed")
    }
}}

vadian · Accepted Answer · 2020-01-15T05:37:45.973

Of course you have to assign values to the idx attribute and you have to assign the result of the fetch to the label.

First replace

let appDelegate = UIApplication.shared.delegate as! AppDelegate //Singlton instanc
var context:NSManagedObjectContext!

with

lazy var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

Then replace both openDatabse and saveData with

func openDatabse()
{
    let names = ["kim kardashian", "jessica biel", "Hailey Rienhart"]
    for i in 0..<names.count {
        let newUser = Users(context: context)
        newUser.name = names[i]
        newUser.idx = Int32(i + 1)
    }
    print("Storing Data..")
    do {
        try context.save()
    } catch {
        print("Storing data Failed", error)
    }
}

Finally add a line in joke to display the value

func joke(at index : Int) {
    let fetchRequest = NSFetchRequest<Users>(entityName: "Users")
    fetchRequest.predicate = NSPredicate(format: "idx == %d", Int32(index))
    do {
        if let user = try context.fetch(fetchRequest).first {
            labelName.text = user.username
        }
    } catch {
        print("Could not fetch \(error) ")
    }
}

It creates the records and assigns the proper indexes. Then entering a number in the text field should work.

But – once again – on each launch of the app the 3 records are inserted again with the same names and indexes. Be aware of that!

I edited my code above with your code. Still have the same issue nothing happens when I enter a number in the textfield. Nothing happens. Nothing changes on the label. Thanks for your help so far!. — , Jan 15 '20 at 21:10
Please don't edit the question with code from the answer. The question makes no sense anymore for others. Did you connect the delegate of the text field in Interface Builder to the controller? You have to otherwise the delegate method won't be called. — vadian, Jan 15 '20 at 21:14
If I hold down control then click on the textfield then drag it to the top left button on story and click delegate. Nothing changes. — , Jan 16 '20 at 01:20
I added enterT.delegate = self in videwdidload and still nothing changes. — , Jan 16 '20 at 04:01
I changed the textfield method to shouldChangeCharactersIn and it work — , Jan 16 '20 at 04:06

Use core data index to fetch a specific item from core data

1 Answers1