Add Item to Specific Table View Row if Available - ios

Question

I am trying to create a tableView of users from my Parse database that are in the same class (at school). All users have to have a username, but not all will have given the app their full name or set a profile picture. I use this code:
let studentsQuery = PFQuery(className:"_User")
studentsQuery.whereKey("objectId", containedIn: studentsArray! as! [AnyObject])
let query2 = PFQuery.orQueryWithSubqueries([studentsQuery])
query2.findObjectsInBackgroundWithBlock {
(results: [PFObject]?, error: NSError?) -> Void in
if error != nil {
// Display error in tableview
} else if results! == [] {
spinningActivity.hideAnimated(true)
print("error")
} else if results! != [] {
if let objects = results {
for object in objects {
if object.objectForKey("full_name") != nil {
let studentName = object.objectForKey("full_name")! as! String
self.studentNameResults.append(studentName)
}
if object.objectForKey("username") != nil {
let studentUsername = object.objectForKey("username")! as! String
self.studentUsernameResults.append(studentUsername)
}
if object.objectForKey("profile_picture") != nil {
let studentProfilePictureFile = object.objectForKey("profile_picture") as! PFFile
studentProfilePictureFile.getDataInBackgroundWithBlock({ (image: NSData?, error: NSError?) in
if error == nil {
let studentProfilePicture : UIImage = UIImage(data: image!)!
self.studentProfilePictureResults.append(studentProfilePicture)
} else {
print("Can't get profile picture")
// Can't get profile picture
}
self.studentsTableView.reloadData()
})
spinningActivity.hideAnimated(true)
} else {
// no image
}
}
}
} else {
spinningActivity.hideAnimated(true)
print("error")
}
}
This code works fine if all of the users have a username, full_name, and a profile_picture. I can't figure out, however, how to get a tableView of the usernames of a user and add a user's name or picture to the user's corresponding tableViewCell only if the user has a picture. Here is how my tableView is configured:
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return studentUsernameResults.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("studentsCell", forIndexPath: indexPath) as! StudentsInClassInformationTableViewCell
cell.studentProfilePictureImageView.layer.cornerRadius = cell.studentProfilePictureImageView.frame.size.width / 2
cell.studentProfilePictureImageView.clipsToBounds = true
cell.studentProfilePictureImageView.image = studentProfilePictureResults[indexPath.row]
cell.studentUsernameLabel.text = studentUsernameResults[indexPath.row]
cell.studentNameLabel.text = studentNameResults[indexPath.row]
return cell
}
The studentProfilePictureResults, studentUsernameResults, and studentNameResults come from arrays of the user's picture, username, and name results pulled from Parse. If a user does not have a profile picture, I get the error, Index is out of range. Obviously, this means that there are, say, three names, three usernames, and only two pictures and Xcode doesn't know how to configure the cell. My question: How can I set a tableView up of a user's username and place their name and profile picture in the same cell, only if they have one?

Answer 1

Trying to store the different attributes in different arrays will be a problem, since as you have found, you end up with problems where a particular user doesn't have an attribute. You could use an array of optionals, so that you could store nil for an absent attribute, but it is much simpler to store the PFObject itself in a single array and accessing the attributes in cellForRowAtIndexPath rather than splitting out the attributes.
Since fetching the photo requires a separate, asynchronous, operation, you can store it separately. Rather than using an array to store the retrieved photos, which would have the same problem of ordering, you can use a dictionary, indexed by the user id; although for a large number of students it would probably be more efficient to use something like SDWebImage to download the photos as required in cellForRowAtIndexPath.
// these are instance properties defined at the top of your class
var students: [PFObject]?
var studentPhotos=[String:UIImage]()
// This is in your fetch function
let studentsQuery = PFUser.Query()
studentsQuery.whereKey("objectId", containedIn: studentsArray! as! [AnyObject])
let query2 = PFQuery.orQueryWithSubqueries([studentsQuery])
query2.findObjectsInBackgroundWithBlock {
(results: [PFObject]?, error: NSError?) -> Void in
guard (error == nil) else {
print(error)
spinningActivity.hideAnimated(true)
return
}
if let results = results {
self.students = results
for object in results {
if let studentProfilePictureFile = object.objectForKey("profile_picture") as? PFFile {
studentProfilePictureFile.getDataInBackgroundWithBlock({ (image: NSData?, error: NSError?) in
guard (error != nil) else {
print("Can't get profile picture: \(error)")
return
}
if let studentProfilePicture = UIImage(data: image!) {
self.studentPhotos[object["username"]!]=studentProfilePicture
}
}
}
spinningActivity.hideAnimated(true)
self.tableview.reloadData()
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if self.students != nil {
return self.students!.count
}
return 0
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("studentsCell", forIndexPath: indexPath) as! StudentsInClassInformationTableViewCell
cell.studentProfilePictureImageView.layer.cornerRadius = cell.studentProfilePictureImageView.frame.size.width / 2
cell.studentProfilePictureImageView.clipsToBounds = true
let student = self.students[indexPath.row]
if let studentPhoto = self.studentPhotos[student["username"]!] {
cell.studentProfilePictureImageView.image = studentProfilePictureResults[indexPath.row]
} else {
cell.studentProfilePictureImageView.image = nil
}
cell.studentUsernameLabel.text = student["username"]!
if let fullName = student["full_name"] {
cell.studentNameLabel.text = fullName
} else {
cell.studentNameLabel.text = ""
return cell
}
A few other pointers;
The use of _ to separate words in field names isn't really used in the iOS world; camelCase is preferred, so fullName rather than full_name
It looks like your Parse query could be more efficient if you had a class field or reference object so that you didn't need to supply an array of other class members.