Unexpectedly found nil while unwrapping... MessageKit - ios

Question

I have a struct set up for Messages and each time I got to load messages in app, I receive an unexpectedly found nil error on this line of code -->
var chatPartnerId: String {
return isFromCurrentUser ? toID! : fromID! // where I get the error
}
I can't figure out what Im doing wrong here at all.
Here's the class setup:
struct Message: MessageType {
let id: String?
var messageId: String {
return id ?? UUID().uuidString
}
var content: String?
var toID: String?
var fromID: String?
var isFromCurrentUser = Bool()
var chatPartnerId: String {
return isFromCurrentUser ? toID! : fromID!
}
let sentDate: Date
let sender: SenderType
var image: UIImage?
var downloadURL: URL?
var kind: MessageKind {
if let image = image {
let mediaItem = ImageMediaItem(image: image)
return .photo(mediaItem)
} else {
return .text(content ?? "")
}
}
init(user: User, content: String, fromID: String, toID: String) {
sender = Sender(senderId: user.uid!, displayName: user.name!)
self.content = content
self.fromID = fromID
self.toID = toID
sentDate = Date()
id = nil
}
init(user: User, image: UIImage) {
sender = Sender(senderId: user.uid!, displayName: user.name!)
self.image = image
content = ""
fromID = ""
toID = ""
sentDate = Date()
id = nil
}
init?(document: QueryDocumentSnapshot) {
let data = document.data()
guard
let sentDate = data["created"] as? Timestamp,
let senderId = data["senderId"] as? String,
let fromID = data["fromID"] as? String,
let toID = data["toID"] as? String,
let senderName = data["senderName"] as? String
else {
return nil
}
id = document.documentID
self.sentDate = sentDate.dateValue()
sender = Sender(senderId: senderId, displayName: senderName)
self.isFromCurrentUser = fromID == Auth.auth().currentUser?.uid
if let content = data["content"] as? String {
self.content = content
downloadURL = nil
} else if let urlString = data["url"] as? String, let url = URL(string: urlString) {
downloadURL = url
content = ""
} else {
return nil
}
}
}
// MARK: - DatabaseRepresentation
extension Message: DatabaseRepresentation {
var representation: [String: Any] {
var rep: [String: Any] = [
"created": sentDate,
"senderId": sender.senderId,
"fromID": fromID,
"toID": toID,
"senderName": sender.displayName
]
if let url = downloadURL {
rep["url"] = url.absoluteString
} else {
rep["content"] = content
}
return rep
}
}
// MARK: - Comparable
extension Message: Comparable {
static func == (lhs: Message, rhs: Message) -> Bool {
return lhs.id == rhs.id
}
static func < (lhs: Message, rhs: Message) -> Bool {
return lhs.sentDate < rhs.sentDate
}
}

Answer 1

Both toID and fromID are optionals and may be nil. Avoid force unwrapping the optional (and actually avoid force unwrapping anything else, with very rare exceptions), like you do in the problematic statement.
Instead, you can:
Don't be afraid to return an optional:
var chatPartnerId: String? { // <-- returns optional
return isFromCurrentUser ? toID : fromID
}
In many cases it's much better to deal with the nil as a condition that helps you understand the state of the app. For example nil may mean you should skip the processing of such message.
You can return a default bogus ID, or an empty string:
var chatPartnerId: String {
guard let id = isFromCurrentUser ? toID : fromID else {
return "" // <-- returns bogus ID
}
return id
}
You can change the property to be required:
var toID: String // <-- not optional
var fromID: String // <-- not optional
Looking at all of your inits I see none of them allows these paramters to be nil. So you don't need to make them optional.