Swift UIImageView Firebase DispatchQueue - swift

Question

I am using firebase to save and load my images. I have created a new view in Xcode and am using the same code I have been using to load profile images. Yet, this is now throwing an error saying that the url string is nil. The image url data disappears after "DispatchQueue.global().async". What could be causing this and how could I track this? Very strange how this code works for other views yet for this new view it is throwing an error.
let businessProfilePicture = dictionary["profPicString"] as! String
if businessProfilePicture.count > 0 {
let url = URL(string: businessProfilePicture)
print(url)
print("printing the url here to check")
DispatchQueue.global().async {
let dataURL = try? Data(contentsOf: url!)
print(dataURL)
print("printing the data url here")
DispatchQueue.main.async {
print(dataURL)
print("Printing Data to check")
let image = UIImage(data: dataURL!)?.potter_circleo
self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
self.businessProfilePicture.image = image
}
}
Full Code
func getWorkLocation() {
let uid = Auth.auth().currentUser?.uid
var profPicURL: String = ""
Database.database().reference().child("employees").child(uid!).child("Business").observe(.value, with: { snapshot in
if snapshot.exists() {
let dictionary = snapshot.value as? NSDictionary
self.businessName.text = dictionary?["businessName"] as? String
self.businessStreet.text = dictionary?["businessStreet"] as? String
self.businessCity.text = dictionary?["businessCity"] as? String
profPicURL = dictionary?["profPicString"] as! String
// set image
if profPicURL.count > 0 {
let url = URL(string: profPicURL)
DispatchQueue.global().async {
let data = try? Data(contentsOf: url!)
DispatchQueue.main.async {
let image = UIImage(data: data!)?.potter_circle
self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
self.businessProfilePicture.image = image
}
}
} else {
let image = UIImage(named: "profile picture")?.potter_circle
self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
self.businessProfilePicture.image = image
}
} else {
self.businessName.text = ""
self.businessStreet.text = "Go to Add Work Location to send request"
self.businessCity.text = ""
self.deleteButton.isEnabled = false
}
})
}

Answer 1

Are you certain that the URL you create from profPicURL is being created properly?
URL(string:) can fail and return nil. If you then go on to implicitly unwrap it in Data(contentsOf: url!) you will crash.
Similarly, try? Data(contentsOf: url) can return nil. If it does, then when you implicitly unwrap it in UIImage(data: data!) you will crash.
As Jacob said in comments, you need to learn more about implicitly unwrapped optionals. To get you started, you might structure your code something like this:
if let url = URL(string: profPicURL) {
DispatchQueue.global().async {
if let data = try? Data(contentsOf: url),
let image = UIImage(data: data)?.potter_circle
{
DispatchQueue.main.async {
self.businessProfilePicture.contentMode = UIView.ContentMode.scaleAspectFill
self.businessProfilePicture.image = image
}
} else {
// raise an an error or set self.businessProfilePicture.image to a generic image or something
}
}
} else {
// raise an an error or set self.businessProfilePicture.image to a generic image or something
}