core data insert big data in background

Question

I want my application to load all server information to Core Data entity in background. I have created new entity called 'Event' then created 5 attributes in it. Also, I created NSManagedObject subclass for my entity:

import Foundation
import CoreData

@objc(Event)
class Event: NSManagedObject {

    @NSManaged var category: String
    @NSManaged var date: String
    @NSManaged var event: String
    @NSManaged var location: String
    @NSManaged var time: String
}

And here is how I'm loading all data and want to insert it to core data entity:

func loadAllData(){
    println("loading all data")

    let params = ServerConstants.infoParam + "=true"

    // creating request, set its method to POST and append params to request
    var request = NSMutableURLRequest(URL: NSURL(string: ServerConstants.getInfoURL)!)
    request.HTTPMethod = "POST"
    request.HTTPBody = params.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)

    // start loading data in background
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
        var session = NSURLSession.sharedSession()
        var task = session.dataTaskWithRequest(request){ (data, response, error) -> Void in
            if error == nil {
                let json = JSON(data: data)
                self.defaults.setObject(json["lastCategoriesId"].string, forKey: "lastCategoriesId")
                self.defaults.setObject(json["lastEventsId"].string, forKey: "lastEventsId")

                //println(json)
                var maxValue = Float(json["categories"].count + json["events"].count)
                println("maxself. - \(maxValue)")

                var error: NSError?
                var array = json["events"]

                let newItem = NSEntityDescription.insertNewObjectForEntityForName("Event", inManagedObjectContext: self.managedObjectContext!) as! Event

                for var i: Int = 0; i < array.count; i++ {                        
                    newItem.category = array[i]["category"].string!
                    newItem.event = array[i]["event"].string!
                    newItem.location = array[i]["location"].string!
                    newItem.date = array[i]["date"].string!
                    newItem.time = array[i]["time"].string!

                    println(i)
                }
                if !self.managedObjectContext!.save(&error) {
                    println("Could not save \(error), \(error?.userInfo)")
                }
                println("done")
            }
        }
        task.resume()
    }
}

The problem is that my for loop is working very slow. One iteration is ~1 second. What am I doing wrong? The data is about 3500 rows.

Here is my json:

{
    "lastEventsId" : "3602",
    "events" : [
        {
            "date" : "lorem",
            "time" : "ipsum",
            "event" : "dolor",
            "category" : "sit",
            "location" : "amet"
        },...
}

I tried to run this for loop:

for var i: Int = 0; i < array.count; i++ {
    println(i)
}

and again it is working 1 iteration for 1 second. But if I just put index max length as 3500 it iterate the whole loop for ~1 sec.

for var i: Int = 0; i < 3500; i++ {
    println(i)
}

Answer 1

maybe swift is calculating everytime the array.count, same as php count(array) try define array.count in a const

 let limit = array.count;
 for i in 0..<limit {
    //do your stuff
 }