Single UITableView with different custom UITableViewCells issue - ios

Question

I have added UITableView into UIScrollView, I have created an IBOutlet for height constraint of UITableView which helps me in setting the content size of UITableview.
I have 3 tabs and I switch tabs to reload data with different data source . Also the i have different custom cells when the tab changes.
So when the tab changes I call reloadData
here is my cellForRow function
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Configure the cell...
var cell:UITableViewCell!
let event:Event!
if(tableView == self.dataTableView)
{
let eventCell:EventTableViewCell = tableView.dequeueReusableCellWithIdentifier(kCellIdentifier, forIndexPath: indexPath) as! EventTableViewCell
eventCell.delegate = self
event = sectionsArray[indexPath.section].EventItems[indexPath.row]
eventCell.eventTitleLabel?.text = "\(event.title)"
eventCell.eventImageView?.image = UIImage(named: "def.png")
if let img = imageCache[event.imgUrl] {
eventCell.eventImageView?.image = img
}
else {
print("calling image of \(indexPath.row) \(event.imgUrl)")
// let escapedString = event.imgUrl.stringByAddingPercentEncodingWithAllowedCharacters(.URLHostAllowedCharacterSet())
let session = NSURLSession.sharedSession()
do {
let encodedImageUrl = CommonEHUtils.urlEncodeString(event.imgUrl)
let urlObj = NSURL(string:encodedImageUrl)
if urlObj != nil {
let task = session.dataTaskWithURL(urlObj!, completionHandler: { ( data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
guard let realResponse = response as? NSHTTPURLResponse where
realResponse.statusCode == 200 else {
print("Not a 200 response, url = " + event.imgUrl)
return
}
if error == nil {
// Convert the downloaded data in to a UIImage object
let image = UIImage(data: data!)
// Store the image in to our cache
self.imageCache[event.imgUrl] = image
// Update the cell
dispatch_async(dispatch_get_main_queue(), {
if let cellToUpdate:EventTableViewCell = tableView.cellForRowAtIndexPath(indexPath) as? EventTableViewCell {
cellToUpdate.eventImageView?.image = image
}
})
}
})
task.resume()
}
} catch {
print("Cant fetch image \(event.imgUrl)")
}
}
cell = eventCell
}
else if(secodTabClicked)
{
let Cell2:cell2TableViewCell = tableView.dequeueReusableCellWithIdentifier(CellIdentifier1, forIndexPath: indexPath) as! cell2TableViewCell
//Image loading again takes place here
cell = Cell2
}
else if(thirdTabClicked)
{
let Cell3:cell3TableViewCell = tableView.dequeueReusableCellWithIdentifier(CellIdentifier2, forIndexPath: indexPath) as! cell3TableViewCell
//Image loading again takes place here
cell = Cell3
}
return cell
}
As you can see each tab has different custom cells with images.
Below are the problems I am facing
1) it takes time to reload data when I switch tabs and their is considerable lag time. On iphone 4s it is worse
2) When I open this page, first tab is selected by default, so when i scroll, everything works smoothly. But when i switch tabs, and when i scroll again after reloading of data, the scroll becomes jerky and immediately i get memory warning issue.
What I did so far?
1) I commented the image fetching code and checked whether that is causing jerky scroll, but its not.
2) I used time profiler, to check what is taking more time, and it points the "dequeueReusableCellWithIdentifier". So I dont know what is going wrong here.

Answer 1

Your code does not look "symmetric" with respect to cell set up when secodTabClicked and thirdTabClicked. I do not see firstTabClicked, and it looks to me that the condition that you are using to determine which tab is clicked overlaps with secodTabClicked and thirdTabClicked. In other words, you are probably getting into the top branch, and return EventTableViewCell when cell2TableViewCell or cell3TableViewCell are expected.
Refactoring your code to make type selection "symmetric" with respect to all three cell types should fix this problem.
Another solution could be making separate data sources for different tabs, and switching the data source instead of setting xyzTabClicked flags. You would end up with thee small functions in place of one big function, which should make your code easier to manage.