Use Core Data to Insert data asynchronously in Swift with UIProgressView

Question

I receive a JSon that I convert to a array of dictionaries and insert this array to Core Data.

The result of this Array has 8.000 items.

How to insert an UIProgressView while the Core Data is working with the code bellow?

Thank you!

func CreateContext() -> NSManagedObjectContext {
    let AppDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let Context: NSManagedObjectContext = AppDel.managedObjectContext
    return Context
}

static func AddData(arrayDictionary: [[String : AnyObject]]) {
    for Item in arrayDictionary {
        let Context = CreateContext()
        let DAO = NSEntityDescription.insertNewObjectForEntityForName("Customers", inManagedObjectContext: Context)

        // Insert at Core Data
        if let item = Item["UserID"] as? Int {
            DAO.setValue(item, forKey: "userID")
        }
        if let item = Item["Name"] as? String {
            DAO.setValue(item, forKey: "name")
        }
        if let item = Item["Email"] as? String {
            DAO.setValue(item, forKey: "email")
        }

        do {
            try Contexto.save()
        } catch {
            let nserror = error as NSError
            //abort()
        }
        }
    }
}

EDIT

The data is being inserted by a custom class. I tried to create a Protocol and Delegate but I don't know where is the error (sincerely, I don't know how to work with Protocol and Delegate. I tried to follow the example in Howto Update a gui (progressview) from a download delegate in swift)

My ViewController class:

import UIKit

protocol ProgressBarDelegate: class {
    func UpdateProgressBar(progress: Float)
}

class MyViewController: UIViewController {

    @IBOutlet var progressView: UIProgressView!

    func AddDataFromArray() {
        let DB = MyCustomClass()
        DB.delegate?.UpdateProgressBar(progressView.progress)
        DB.AddData(getArrayDictionaryData())
    }

}

My Custom class:

class MyCustomClass {

    var delegate: ProgressBarDelegate?

    func initWithDelegate(delegate: ProgressBarDelegate) {
        self.delegate = delegate
    }

    func CreateContext() -> NSManagedObjectContext {
        let AppDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
        let Context: NSManagedObjectContext = AppDel.managedObjectContext
        return Context
    }

    func AddData(arrayDictionary: [[String : AnyObject]]) {
        var addedItems: Int = 0
        var Progress = Float()

        for Item in arrayDictionary {
        addedItems += 1
        Progress = ((Float(100.0) / Float(arrayDictionary.count)) * Float(addedItems)) / Float(100)

            let Context = CreateContext()
            let DAO = NSEntityDescription.insertNewObjectForEntityForName("Customers", inManagedObjectContext: Context)

            // Insert at Core Data
            if let item = Item["UserID"] as? Int {
                DAO.setValue(item, forKey: "userID")
            }
            if let item = Item["Name"] as? String {
                DAO.setValue(item, forKey: "name")
            }
            if let item = Item["Email"] as? String {
                DAO.setValue(item, forKey: "email")
            }

            do {
                try Contexto.save()
            } catch {
                let nserror = error as NSError
                //abort()
            }

            delegate!.UpdateProgressBar(Progress)
        }
    }
}

@Wain : I just added more code to explain better what I want. Basically, I'm calling the method AddData from other class. This method is in a custom class. Thank you! — Sergio Costa Faria, Nov 20 '15 at 12:19

score 1 · Accepted Answer · answered Nov 20 '15 at 14:52

You seem to be misunderstanding the relationships a little bit.

A class can take a delegate if it requires some information to be supplied or wants to make a callback to let someone know that something happened. The delegate implements the methods specified in the delegate protocol and handles the notifications:

Delegate (observer)
  -> conforms to the delegate protocol
  -> registers itself
  -> handles notifications

Interesting class
  -> holds a reference to a delegate
  -> notifies the delegate when things happen

In your case. MyViewController should conform to the delegate protocol, so it should implement UpdateProgressBar. It creates an instance of MyCustomClass to do some work for it and sets itself as the delegate. MyCustomClass then does some work and calls UpdateProgressBar, where MyViewController then updates the UI.

You get a crash at the moment because you never set the delegate. This line:

DB.delegate?.UpdateProgressBar(progressView.progress)

should be

DB.delegate = self

aside:

Don't call something CreateContext if it isn't actually creating something. Also, the first letter of functions should be lower case.

Thank you so much @Wain! That's working now! (and I came from ASP.Net/VB, that's why my methods has the first letter in uppercase, but I'll change it from now). — Sergio Costa Faria, Nov 20 '15 at 17:46

score 0 · Answer 2 · answered Nov 19 '15 at 18:44

Assuming that the progress view already exists, you'd do something like:

self.progressView.progress = 0

for (index, item) in arrayDictionary.enumerate() {
    // Do all the work of importing the data...

    let progress = CGFloat(index) / CGFloat(arrayDictionary.count)
    self.progressView.progress = progress
}

The value of progress will gradually work its way up from nearly zero to 1.0 as the loop keeps executing.

Use Core Data to Insert data asynchronously in Swift with UIProgressView

2 Answers2