Update Table View in iOS (Swift)

Question

I am making a cocktail iOS application.

I am adding strings to a tableview (an ingredient to the "cabinet"). The user enters an ingredient and then presses the button ADD. It successfully adds it to the Core Data but it does not appear right away. What am I doing wrong?

Below is my code, thanks!

ViewController:

import UIKit
import CoreData

class CabinetViewController: UIViewController, UITextFieldDelegate, UITableViewDataSource, UITableViewDelegate {

    var ingredientArray = [String]()
    var display = [String]()
    var dbIngredients = [String]()

    let ingredientFetch = NSFetchRequest(entityName: "Cabinet")
    var fetchedIngredient = [Cabinet]()

    @IBOutlet weak var TextUI: UITextField!
    @IBOutlet weak var Button: UIButton!
    @IBOutlet weak var TableView: UITableView!

    let moc = DataController().managedObjectContext

    override func viewDidLoad() {
        super.viewDidLoad()

        TextUI.delegate = self
        TextUI.addTarget(self, action: "textFieldDidChange:", forControlEvents: UIControlEvents.EditingChanged)

        TableView.delegate = self
        TableView.dataSource = self
        TableView.registerClass(UITableViewCell.self,
            forCellReuseIdentifier: "Cell")

        // fetch Core Data
        do{
            fetchedIngredient = try moc.executeFetchRequest(ingredientFetch) as! [Cabinet]
        } catch {
            fatalError()
        }

        let postEndpoint: String = "http://www.thecocktaildb.com/api/json/v1/1/list.php?i=list"

        guard let url = NSURL(string: postEndpoint) else {
            print("Error: cannot create URL")
            return
        }

        let urlRequest = NSURLRequest(URL: url)
        let config = NSURLSessionConfiguration.defaultSessionConfiguration()
        let session = NSURLSession(configuration: config)

        let task = session.dataTaskWithRequest(urlRequest, completionHandler: { (data, response, error) in
            guard let responseData = data else {
                print("Error: did not receive data")
                return
            }
            guard error == nil else {
                print("error calling GET on www.thecocktaildb.com")
                print(error)
                return
            }

            let post: NSDictionary
            do {
                post = try NSJSONSerialization.JSONObjectWithData(responseData,
                    options: []) as! NSDictionary
            } catch  {
                print("error trying to convert data to JSON")
                return
            }

            var count = 1
            if let drinks = post["drinks"] as? [NSDictionary] {
                for drink in drinks {
                    if let strIngredient = drink["strIngredient1"] as? String {
                        print(String(count) + ". " + strIngredient)
                        self.dbIngredients.append(strIngredient)
                        count++
                    }
                }
            }
        })
        task.resume()
        TableView.reloadData()
    }

    func textFieldDidChange(textField: UITextField) {
        search(self.TextUI.text!)
    }

    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        Button.addTarget(self, action: "buttonPressed:", forControlEvents: .TouchUpInside)
        return true
    }

    func buttonPressed(sender: UIButton!) {
        //ingredientArray.append(TextUI.text!)

        let entity = NSEntityDescription.insertNewObjectForEntityForName("Cabinet", inManagedObjectContext: moc) as! Cabinet
        entity.setValue(TextUI.text!, forKey: "ingredient")
        do{
            try moc.save()
        }catch {
            fatalError("failure to save context: \(error)")
        }
        showAlertButtonTapped(Button)
//        dispatch_async(dispatch_get_main_queue(), { () -> Void in
//            self.TableView.reloadData()
//        })
    }

    @IBAction func showAlertButtonTapped(sender: UIButton) {
        // create the alert
        let alert = UIAlertController(title: "Added!", message: "You've added " + TextUI.text! + " to your cabinet", preferredStyle: UIAlertControllerStyle.Alert)
        // add an action (button)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
        // show the alert
        self.presentViewController(alert, animated: true, completion: nil)
    }

    func search(str:String) {
        display.removeAll(keepCapacity: false)

        for s in dbIngredients{
            if s.hasPrefix(str){
                display.append(s)
                print(s)
            }
        }
    }

    func tableView(tableView: UITableView,
        numberOfRowsInSection section: Int) -> Int {
            return fetchedIngredient.capacity
    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
        do{
            let fetchedIngredient = try moc.executeFetchRequest(ingredientFetch) as! [Cabinet]
            cell.textLabel?.text = fetchedIngredient[indexPath.row].ingredient
        } catch {
            fatalError("bad things happened: \(error)")
        }
        return cell
    }

    func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        tableView.deselectRowAtIndexPath(indexPath, animated: true)

        let alert = UIAlertController(title: "Remove " + fetchedIngredient[indexPath.row].ingredient!,
            message: "No more " + fetchedIngredient[indexPath.row].ingredient! + " in your cabinet?",
            preferredStyle: .Alert)

        let deleteAction = UIAlertAction(title: "Remove",
            style: .Default,
            handler: { (action:UIAlertAction) -> Void in
                self.fetchedIngredient.removeAtIndex(indexPath.row)

                do{
                    let fetchedResults = try self.moc.executeFetchRequest(self.ingredientFetch)
                    if let result = fetchedResults[indexPath.row] as? NSManagedObject {
                        self.moc.deleteObject(result)
                        try self.moc.save()
                    }
                }catch{
                    fatalError()
                }
        })

        let cancelAction = UIAlertAction(title: "Cancel",
            style: .Default) { (action: UIAlertAction) -> Void in
        }

        alert.addAction(cancelAction)
        alert.addAction(deleteAction)

        presentViewController(alert,
            animated: true,
            completion: nil)
        TableView.reloadData()
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    /*
    // MARK: - Navigation
    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // Get the new view controller using segue.destinationViewController.
    // Pass the selected object to the new view controller.
    }
    */
}

Answer 1

Since your problem isn't Core Data you need to use Table View beginUpdates and EndUpdates to insert the row. At the end of your buttonPressed function put this:

do{
    fetchedIngredient = try moc.executeFetchRequest(ingredientFetch) as! [Cabinet]
    self.tableView.beginUpdates()
    let totalIngredients = fetchedIngredient.count
    let newItemIndexPath = NSIndexPath(forRow: totalIngredients-1, inSection: 0)
    self.tableView.insertRowsAtIndexPaths([newItemIndexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
    self.tableView.endUpdates()
} catch {
    fatalError()
}

On your number of rows in section:

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return fetchedIngredient.count
}

And on the cell for row at index path

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
    cell.textLabel?.text = fetchedIngredient[indexPath.row].ingredient
    return cell
}

Answer 2

There are a couple of problems with your code. Firstly, since you're fetching records into an array, calling reloadData will not have any impact unless you update the array. There is no automatic connection between adding a new core data record and your fetchedIngredient array.

There are a few ways to solve this, although the most common is probably to just refetch the records into the same array whenever core data is updated. Alternatively you can change your code to us NSFetchedResultsController instead of an array, which will automatically update the tableView when core data is updated (based on the predicate you provide it). This class provides the automatic connection to core data for you.

Another problem is that you are refetching the records in cellForRowAtIndexPath and didSelectRowAtIndexPath. This should not be done. Instead you should just be referring to the class-level fetchedIngredient array (or the NSFetchedResultsController if you choose to use that).

Furthermore, the call to dataTaskWithRequest runs in the background. It's not clear from the code how you're using it, but the fact that you have reloadData afterwards suggests it should impact the tableView. However because the task runs in the background, the completion handler will run after the table is reloaded. Therefore you should be calling reloadData inside the completion handler. And since it would then be running on another thread, you would have to dispatch it to the main queue, using:

dispatch_async(dispatch_get_main_queue()) {
  self.tableView.reloadData()
}