Refactor cellForRowIndexPath in UITableView Swift - ios

Question

I have a rather long cellForRowAtIndexPath function. I am using parse as my backend and have a lot going on. I want to extract a lot of these conditions and put them in their own functions. Especially the PFUser query, but unfortunately I don't know whats the best way to go about it since I don't know how I can access the elements of each cell in those functions I want to write.
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("PostCells", forIndexPath: indexPath) as! NewsFeedTableCellTableViewCell
// Configure the cell...
// A drive is a post
let drive: PFObject = self.timelineData[indexPath.row] as PFObject
var driverId = drive.objectForKey("driver")!.objectId!
var currentUserObjectId = PFUser.currentUser()!.objectId
if(driverId != currentUserObjectId){
cell.requestButton.layer.borderWidth = 1
cell.requestButton.titleLabel!.font = UIFont.systemFontOfSize(11)
cell.requestButton.tintColor = UIColor.orangeColor()
cell.requestButton.layer.borderColor = UIColor.orangeColor().CGColor
cell.requestButton.setTitle("REQUEST", forState: UIControlState.Normal)
}
else {
cell.requestButton.layer.borderWidth = 1
cell.requestButton.titleLabel!.font = UIFont.systemFontOfSize(11)
cell.requestButton.tintColor = UIColor.grayColor()
cell.requestButton.layer.borderColor = UIColor.lightGrayColor().CGColor
cell.requestButton.setTitle("REQUEST", forState: UIControlState.Normal)
cell.requestButton.enabled = false
}
// Setting up the attributes of the cell for the news feed
cell.driveTitleTextField.text = drive.objectForKey("title") as! String
cell.wayTextField.text = drive.objectForKey("way") as! String
var departureDate = NSDate()
departureDate = drive.objectForKey("departureDate") as! NSDate
var dateFormat = NSDateFormatter()
dateFormat.dateFormat = "M/dd hh:mm a"
cell.departureDateTextField.text = dateFormat.stringFromDate(departureDate)
if((drive.objectForKey("way")!.isEqualToString("Two Way")))
{
var returnDate = NSDate()
returnDate = drive.objectForKey("returnDate") as! NSDate
cell.returningDateTextField.text = dateFormat.stringFromDate(returnDate)
}
else if((drive.objectForKey("way")!.isEqualToString("One Way")))
{
cell.returningDateTextField.enabled = false
cell.returningDateTextField.userInteractionEnabled = false
cell.returningDateTextField.hidden = true
cell.returningLabel.hidden = true
}
var seatNumber = NSNumber()
seatNumber = drive.objectForKey("seatNumber") as! NSInteger
var numberFormat = NSNumberFormatter()
numberFormat.stringFromNumber(seatNumber)
cell.seatNumberTextField.text = numberFormat.stringFromNumber(seatNumber)
// this is a PFUser query so we can get the users image and name and email from the User class
var findDrive = PFUser.query()
var objectId: AnyObject? = drive.objectForKey("driver")!.objectId!
findDrive?.whereKey("objectId", equalTo: objectId!)
findDrive?.findObjectsInBackgroundWithBlock{
(objects:[AnyObject]?, error:NSError?)->Void in
if (error == nil){
if let actualObjects = objects {
let possibleUser = (actualObjects as NSArray).lastObject as? PFUser
if let user = possibleUser {
cell.userProfileNameLabel.text = user["fullName"] as? String
cell.userEmailLabel.text = user["username"] as? String
//Profile Image
cell.profileImage.alpha = 0
if let profileImage = user["profilePicture"] as? PFFile {
profileImage.getDataInBackgroundWithBlock{
(imageData:NSData? , error:NSError?)-> Void in
if(error == nil) {
if imageData != nil{
let image:UIImage = UIImage (data: imageData!)!
cell.profileImage.image = image
}
}
}
}
UIView.animateWithDuration(0.5, animations: {
cell.driveTitleTextField.alpha = 1
cell.wayTextField.alpha = 1
cell.profileImage.alpha = 1
cell.userProfileNameLabel.alpha = 1
cell.userEmailLabel.alpha = 1
cell.seatNumberTextField.alpha = 1
cell.returningDateTextField.alpha = 1
cell.departureDateTextField.alpha = 1
})
}
}
}
}
return cell
}
EDIT 1
I came up with a way to refactor my code that I would like critiqued!
1. I extracted a lot of the cells configurations and put them into to functions, one for the button on the cell and the other for all the data from parse.
func configureDataTableViewCell(cell:NewsFeedTableCellTableViewCell, drive: PFObject)
{
cell.driveTitleTextField.text = drive.objectForKey("title") as! String
cell.wayTextField.text = drive.objectForKey("way") as! String
cell.userEmailLabel.text = drive.objectForKey("username") as? String
cell.userProfileNameLabel.text = drive.objectForKey("name") as? String
var departureDate = NSDate()
departureDate = drive.objectForKey("departureDate") as! NSDate
var dateFormat = NSDateFormatter()
dateFormat.dateFormat = "M/dd hh:mm a"
cell.departureDateTextField.text = dateFormat.stringFromDate(departureDate)
if((drive.objectForKey("way")!.isEqualToString("Two Way")))
{
var returnDate = NSDate()
returnDate = drive.objectForKey("returnDate") as! NSDate
cell.returningDateTextField.text = dateFormat.stringFromDate(returnDate)
}
else if((drive.objectForKey("way")!.isEqualToString("One Way")))
{
cell.returningDateTextField.enabled = false
cell.returningDateTextField.userInteractionEnabled = false
cell.returningDateTextField.hidden = true
cell.returningLabel.hidden = true
}
var seatNumber = NSNumber()
seatNumber = drive.objectForKey("seatNumber") as! NSInteger
var numberFormat = NSNumberFormatter()
numberFormat.stringFromNumber(seatNumber)
cell.seatNumberTextField.text = numberFormat.stringFromNumber(seatNumber)
}
func configureButtonTableViewCell(cell:NewsFeedTableCellTableViewCell, userID: String)
{
var currentUserObjectId = PFUser.currentUser()!.objectId
if(userID != currentUserObjectId){
cell.requestButton.layer.borderWidth = 1
cell.requestButton.titleLabel!.font = UIFont.systemFontOfSize(11)
cell.requestButton.tintColor = UIColor.orangeColor()
cell.requestButton.layer.borderColor = UIColor.orangeColor().CGColor
cell.requestButton.setTitle("REQUEST", forState: UIControlState.Normal)
println("orange")
}
else {
cell.requestButton.layer.borderWidth = 1
cell.requestButton.titleLabel!.font = UIFont.systemFontOfSize(11)
cell.requestButton.tintColor = UIColor.grayColor()
cell.requestButton.layer.borderColor = UIColor.lightGrayColor().CGColor
cell.requestButton.setTitle("REQUEST", forState: UIControlState.Normal)
cell.requestButton.enabled = false
println("gray")
}
}
2. I then passed in the functions from step 1 and into my cellForRowIndexPath
// A drive is a post
let drive: PFObject = self.timelineData[indexPath.row] as PFObject
var driverId : String = drive.objectForKey("driver")!.objectId!!
configureButtonTableViewCell(cell, userID: driverId)
configureDataTableViewCell(cell, drive: drive)
3. I stored all my PFUser data into my object when its saved instead of querying the user class. So I get the PFUser.currentUser() username, full name, and profile picture when they save a post.
My load data has been modified. I store all the profile pictures in there own array.
func loadData(){
var findItemData:PFQuery = PFQuery(className:"Posts")
findItemData.addDescendingOrder("createdAt")
findItemData.findObjectsInBackgroundWithBlock{
(objects:[AnyObject]? , error:NSError?) -> Void in
if error == nil
{
self.timelineData.removeAll(keepCapacity: false)
self.profilePictures.removeAll(keepCapacity: false)
self.timelineData = objects as! [PFObject]
for object in objects! {
self.profilePictures.append(object.objectForKey("profilePicture") as! PFFile)
}
self.newsFeedTableView.reloadData()
}
}
}
And finally, here is my updated cellForRowIndexPath
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell = tableView.dequeueReusableCellWithIdentifier("PostCells", forIndexPath: indexPath) as! NewsFeedTableCellTableViewCell
// Configure the cell...
// A drive is a post
let drive: PFObject = self.timelineData[indexPath.row] as PFObject
var driverId : String = drive.objectForKey("driver")!.objectId!!
configureButtonTableViewCell(cell, userID: driverId)
configureDataTableViewCell(cell, drive: drive)
println(PFUser.currentUser()?.objectForKey("username"))
if let profileImage = drive["profilePicture"] as? PFFile {
profileImage.getDataInBackgroundWithBlock{
(imageData:NSData? , error:NSError?)-> Void in
if(error == nil) {
if imageData != nil{
let image:UIImage = UIImage (data: imageData!)!
cell.profileImage.image = image
}
}
}
}
return cell
}
Let me know what you guys think, I want to do make my code much more readable, fast, and memory efficient.

Answer 1

You shouldn't be doing any heavy model stuff inside cellForRow.
What you're currently trying to do will greatly slow down your UI.
In most cases you will want your model objects setup, and ready to go before you even get to cellForRow.
This means performing your Parse queries somewhere like in viewDidLoad, keep those results in an array, and when it comes time to do so, apply them to your cells in cellForRow. This way, when a user scrolls, a new query won't be dispatched for every new cell that comes into view. It will already be available.
In addition to this, should you need to make any changes to these items once they have been fetched, you can do so, and have them remain unchanged even when the user is scrolling.

Answer 2

Refactor so you have some data type or group of instance variables to serve as a view model. Avoid making asynchronous calls that mutate the cell in cellForRowAtIndexPath. Instead have your data access method mutate or recreate the view model and at the end of your callback, dispatch_async to the main queue. Give it a closure that tells your table view to reloadData and whatever else you need to do for views to show the new data.
Here's a little pseudocode to describe what I mean:
func loadData() {
parseQueryWithCallback() { data in
self.viewModel = doWhateverTransformsAreNeeded(data)
dispatch_async(dispatch_get_main_queue(), self.tableView.reloadData)
}
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) {
let cell = dequeue(...)
cell.thingOne = self.viewModel.things[indexPath.row].thingOne
cell.thingTwo = self.viewModel.things[indexPath.row].thingTwo
return cell
}