after update - Unexpectedly found nil while unwrapping an Optional value - swift

Question

After I've updated my project I get this error:
Unexpectedly found nil while unwrapping an Optional value
class Search {
private var _username: String!
private var _userImg: String!
private var _userKey: String!
private var _userRef: DatabaseReference!
var currentUser = KeychainWrapper.standard.string(forKey: "uid")
var username: String {
return _username <- error
}
var userImg: String {
return _userImg
}
var userKey: String{
return _userKey
}
init(username: String, userImg: String) {
_username = username
_userImg = userImg
}
init(userKey: String, postData: Dictionary<String, AnyObject>) {
_userKey = userKey
if let username = postData["username"] as? String {
_username = username
}
if let userImg = postData["userImg"] as? String {
_userImg = userImg
}
_userRef = Database.database().reference().child("messages").child(_userKey)
}
}
It worked fine under Swift 3 and Firebase 3.0.2, but now, where everything is update, it crashes all the time. It's not a duplicate to any other question as it worked all before.

Answer 1

I am not sure I fully understand the question or what exactly is causing the crash (it's probably a missing child node) or what the use case is of the implicitly unwrapped class vars but in response to a comment, here's what I would do in Swift 4, Firebase 4
Leave your Search class as is except change the init to the following (this is shortened to provide context)
init(withSnap: DataSnapshot) {
_userKey = withSnap.key
let dict = withSnap.value as! [String: Any]
_username = dict["username"] as? String ?? "NO USER NAME!"
_userImg = dict["userImg"] as? String ?? "NO IMAGE"
}
and then the Firebase function to get a user (for example) would look like this
let userRef = self.ref.child("users").child("uid_0")
userRef.observeSingleEvent(of: .value, with: { snapshot in
let mySearch = Search(withSnap: snapshot)
print(mySearch.userKey, mySearch.username, mySearch.userImg)
})
You would need to add in the rest of the class code to assign _userRef etc.
The idea here is to provide default values to the required class properties in case one of the Firebase nodes didn't exist and results in nil. i.e. if uid_0 didn't have a Username child node your class would crash (which it is). With the code above, that property would be set to a default value.
And for thoroughness suppose a user node looks like this
users
uid_0: "some string" //the value here is a String, not a Dictionary
that would crash my code. To prevent that, add more error checking in the init
init(withSnap: DataSnapshot) {
_userKey = withSnap.key
if let dict = withSnap.value as? [String: Any] {
_username = dict["username"] as? String ?? "NO USER NAME!"
_userImg = dict["userImg"] as? String ?? "NO IMAGE"
} else {
_username = "No user data"
_userImg = "No user data"
}
}