UITableViewCell not removed from the UITableView when using reloaddata - ios

Question

I'm using a tableview to display some categories in a left menu. When you select it, the data in the cells changes to courses ('Cursussen') within that category.
Each cell contains an UIImageView and an UILabel.
I noticed a while ago that when you select a course in the left menu, the label will change to that of a category. That wasn't a big issue back then, but now that I'm working to disable certain courses if they are not available it suddenly became a big issue. To indicate a course that's not available, I'm setting label.enabled = false, which works fine, however I also need to prevent the user from tapping on it and navigating to a course that's not available. To do that, I'm using tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) where I check whether the UILabel is enabled. If it's disabled the App won't navigate to the course.
Back to the issue, tapping on a course that is unavailable (which is displaying the correct image and label) will trigger the didSelectRowAtIndexPath delegate, but when I dequeue the Cell and check whether the UILabel in it is disabled it so happens to be enabled instead and furthermore the label.text does not equal the value I see in the App.
State before selecting a row:
State after selecting a row:
cellForRowAtIndexPath method:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath)
-> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("LeftCell", forIndexPath: indexPath)
let label = cell.contentView.subviews[0] as! UILabel
let image = cell.contentView.subviews[1] as! UIImageView
if(selectedCategory.ID > 0 || searchCursusses.count > 0) {
//Category is selected, load course into cell
var cursus : Cursus
if(selectedCategory.ID > 0) {
cursus = cursusses[indexPath.row] as Cursus
} else {
cursus = searchCursusses[indexPath.row] as Cursus
}
image.image = self.chooseImage(false, name: cursus.category!.Name)
label.numberOfLines = 0
label.text = cursus.name
label.lineBreakMode = .ByTruncatingTail
if(defaults.boolForKey("offline-mode")) {
let realm = try! Realm()
let videos = realm.objects(DownloadedVideo).filter("video.cursus.ID = %#", cursus.ID)
if(videos.count > 0) {
label.enabled = true
} else {
label.enabled = false
}
} else {
label.textColor = UIColor.blackColor()
}
cell.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)
cell.setSelected(false, animated: false)
} else {
let category = categories[indexPath.row] as Category
image.image = self.chooseImage(false, name: category.Name)
label.numberOfLines = 0
label.text = category.Name
label.lineBreakMode = .ByTruncatingTail
label.textColor = UIColor.blackColor()
cell.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)
}
return cell
}
didSelectRowAtIndexPath method:
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let cell = tableView.dequeueReusableCellWithIdentifier( "LeftCell", forIndexPath: indexPath)
cell.selectionStyle = .None
if(selectedCategory.ID > 0 || searchCursusses.count > 0) {
let label = cell.contentView.subviews[0] as! UILabel
if(!label.enabled) {
return
}
let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
let resultViewController = storyBoard.instantiateViewControllerWithIdentifier("CursusView") as! CursusViewController
if(selectedCategory.ID > 0) {
resultViewController.loadCursus(self.cursusses[indexPath.row], completionHandler: {
self.presentViewController(resultViewController, animated:true, completion:nil)
})
} else {
resultViewController.loadCursus(self.searchCursusses[indexPath.row], completionHandler: {
self.presentViewController(resultViewController, animated:true, completion:nil)
})
}
} else {
let category = categories[indexPath.row] as Category
cell.setSelected(true, animated: false)
let label = cell.contentView.subviews[0] as! UILabel
let image = cell.contentView.subviews[1] as! UIImageView
if(label.textColor == UIColor.lightGrayColor()) {
return
} else {
image.image = self.chooseImage(true, name: category.Name)
label.numberOfLines = 0
label.text = category.Name
label.textColor = UIColor.whiteColor()
label.lineBreakMode = .ByTruncatingTail
cell.backgroundColor = UIColor(red: 45.0/255.0, green: 145.0/255.0, blue: 220.0/255.0, alpha: 1.0)
self.selectedCategory = category
self.topBarTitle.text = category.Name
let realm = try! Realm()
let cursusses = realm.objects(Cursus).filter("category.ID = %#", selectedCategory.ID)
for cursus in cursusses {
self.cursusses.append(cursus)
}
let title = self.leftMenuNav.subviews[0] as! UILabel
let titleImg = self.leftMenuNav.subviews[1] as! UIImageView
titleImg.image = UIImage(named: "back-icon")
title.text = "Cursussen"
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.tableView.slideInFromRight(0.5)
self.tableView.reloadData()
self.collectionView.crossFade(0.3)
self.collectionView.reloadData()
})
}
}
}
It seems the old cells are not properly cleaned up after calling reloaddata, causing multiple cells to be at the same IndexPath.
I'm at a loss here, please help!

Answer 1

The problem is the line
let cell = tableView.dequeueReusableCellWithIdentifier( "LeftCell", forIndexPath: indexPath)
in the didSelectRowAtIndexPath function because it is creating a new cell (or trying to reuse one) and corrupting the table view cell cache.
You should be getting the existing cell instead using the cellForRowAtIndexPath function.

Answer 2

You have a problem with your approach: didSelectRowAtIndexPath is supposed to look at the data in the model, not in the view. Your code is trying, incorrectly, to access the cell and examine its labels etc. Instead, your method should be accessing the same underlying data source that has been used to make the labels in the first place.
In other words, instead of writing
let label = cell.contentView.subviews[0] as! UILabel
and then examining the enabled/disabled status of the label
you should write
cursus = cursusses[indexPath.row] as Cursus
and examine the availability of the cursus.
One general rule of thumb is that you should get very suspicious when you see code accessing components of UITableViewCell outside cellForRowAtIndexPath. Testing the state of a label is nearly universally an indication that the code is incorrect.

Answer 3

Man you are doing that wrong. Only tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath)
-> UITableViewCell can dequeue cells and setup its contents.
To prevent selection you should react on func tableView(_ tableView: UITableView,
willSelectRowAtIndexPath indexPath: NSIndexPath) -> NSIndexPath and return nil to indicate that you don't want to select anything.
Main problem is that you are writing to complex methods. It is hard to figure out what are you doing and what is you intention. (will/did)SelectRowAtIndexPath should invoke only one/tow some simple methods, for example: perform a segue or load some data.