Data loading from core data to table very slowly - ios

Question

I have table in core data with 100 rows, in tableView I load filtered 25 rows. When I open this UIViewController in app it take near 2 seconds, I think it is very slowly. I test my app on iPhone 5. May be I do something wrong?
I see that cellForRowAtIndexPath method call 4 times for all rows: 1-25, then again 1-25 etc. Is it ok?
When I load just 1 row it works fast.
class TipsViewController: UIViewController, UITableViewDelegate
{
#IBOutlet weak var tableView: UITableView!
var tips = [Tips]()
lazy var managedObjectContext : NSManagedObjectContext? =
{
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
if let managedObjectContext = appDelegate.managedObjectContext
{
return managedObjectContext
}
else {
return nil
}
}()
let defaults = NSUserDefaults.standardUserDefaults()
var languge:String!
override func viewDidLoad()
{
super.viewDidLoad()
languge = defaults.objectForKey("language") as! String
fetchLog()
}
func fetchLog()
{
let fetchRequest = NSFetchRequest(entityName: "Tips")
let sortDescriptor = NSSortDescriptor(key: "id", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
fetchRequest.predicate=NSPredicate(format: "language=%#", languge)
if let fetchResults = managedObjectContext!.executeFetchRequest(fetchRequest, error: nil) as? [Tips]
{
tips = fetchResults
}
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int
{
return 1
}
func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int
{
return tips.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> TipsTableViewCell
{
let cell = tableView.dequeueReusableCellWithIdentifier("cellt", forIndexPath: indexPath) as! TipsTableViewCell
cell.tipsTextView?.text = tips[indexPath.row].textShort
cell.tipsTextView.editable=false
cell.tipsTextView.userInteractionEnabled=false
cell.tipsTextView.textColor = UIColor(red: 0x7E/255, green: 0x7A/255, blue: 0x7F/255, alpha: 1.0)
cell.selectionStyle = UITableViewCellSelectionStyle.Default
return cell
}
func tableView(_tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat
{
let cell = tableView(_tableView, cellForRowAtIndexPath: indexPath)
return cell.getHeight()
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!)
{
if(segue.identifier == "showDetailx"){
var indexPath:NSIndexPath = self.tableView.indexPathForSelectedRow()!
var detailViewController:TipViewController = segue.destinationViewController as! TipViewController
detailViewController.tip = tips[indexPath.row]
}
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath)
{
self.performSegueWithIdentifier("showDetailx", sender: self)
}
func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell,
forRowAtIndexPath indexPath: NSIndexPath)
{
if cell.respondsToSelector("setSeparatorInset:")
{
cell.separatorInset = UIEdgeInsetsZero
}
if cell.respondsToSelector("setPreservesSuperviewLayoutMargins:")
{
cell.preservesSuperviewLayoutMargins = false
}
if cell.respondsToSelector("setLayoutMargins:")
{
cell.layoutMargins = UIEdgeInsetsZero
}
}
}

Answer 1

You have one problem on your estimatedHeightForRowAtIndexPath. You call there cellForRowAtIndexPath, that's why you get another calls to this method. You can remove that code and do the following:
func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat
{
return self.heightForBasicCellAtIndexPath(indexPath)
}
func heightForBasicCellAtIndexPath( indexPath: NSIndexPath) -> CGFloat
{
var sizingCell: UITableViewCell? = nil;
var token: dispatch_once_t = 0
dispatch_once(&token) {
sizingCell = self.tableView.dequeueReusableCellWithIdentifier("cell") as? TipsTableViewCell
}
return sizingCell!.frame.size.height;
}
This method instantiates a sizingCell using GCD to ensure it’s created only once.
Hope this helps

Answer 2

I delete heightForRowAtIndexPath and estimatedHeightForRowAtIndexPath and add to viewDidLoad() this:
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 160.0