Multiple if let statements in Swift and Firebase - swift

Question

I'm trying to compare my responses with other people's responses in the firebase database. My script currently has 2 if statements saying if it's my response, record my answers and then use that to compare against other responses, but it doesn't register my second if statement.
let responsesReference = Database.database().reference().child("responses")
responsesReference.observeSingleEvent(of: .value) { (snapshot: DataSnapshot) in
guard let json = snapshot.value as? [String: Any] else { return }
do {
var similarities = [Similarity]()
for answerElement in json {
if self.currentUser.uid == answerElement.key,
let myanswer = answerElement.value as? [String: Any] {
if self.currentUser.uid != answerElement.key, //DOES NOT REGISTER
let otheranswer = answerElement.value as? [String: Any] {
let percentage = myanswer.similarity(with: otheranswer)
similarities.append(
Similarity(name: answerElement.key, percentage: percentage, answer: otheranswer)
)
}
}
}
self.similarities = similarities.sorted(by: { (a, b) -> Bool in
return a.percentage > b.percentage
})
self.tableView.reloadData()
}

Answer 1

Here's your code properly formatted (I copy and pasted it with no changes other than formatting it)
do {
var similarities = [Similarity]()
for answerElement in json {
if self.currentUser.uid == answerElement.key, let myanswer = answerElement.value as? [String: Any] {
if self.currentUser.uid != answerElement.key, let otheranswer = answerElement.value as? [String: Any] {
let percentage = myanswer.similarity(with: otheranswer)
similarities.append( Similarity(name: answerElement.key, percentage: percentage, answer: otheranswer) )
}
}
Take a look here
if self.currentUser.uid == answerElement.key
and note the next if is nested inside that one
if self.currentUser.uid == answerElement.key
if self.currentUser.uid != answerElement.key
If those two vars are equal in the outside if, they will be equal with the inside if as well so the second check will always fail.
The generic solution is to use and else with your if
if self.currentUser.uid == answerElement.key {
let myanswer = answerElement.value as? [String: Any] <- OPTIONAL!
//do something because they are equal
} else {
let otheranswer = answerElement.value as? [String: Any] <- OPTIONAL!
// do something else because they are NOT equal
}
also note that you've got some optionals in that code and if those go to nil your app will either crash or silently fail with no indication as to why.
The logic isn't exactly clear in this code
let percentage = myanswer.similarity(with: otheranswer)
as each time through the loop
for answerElement in json {
}
there will only be one answer in an answerElement. e.g. there won't be a myAnswer and otherAnswer, there will only be theAnswer. Perhaps there should be a comparison to the prior answer from the loop; I'll expand on that
Here's an example based on reading in all users, getting the answer for this user, removing the user from the results and then comparing that to other users answers. Assume users uid's are used at the key to each user node (which also contains an answer they provides) and we know the auth'd users uid.
let thisUsersUid = "uid_1"
let usersRef = self.ref.child("users") //self.ref points to MY firebase
usersRef.observeSingleEvent(of: .value, with: { snapshot in
var allUsersSnap = snapshot.children.allObjects as! [DataSnapshot]
guard let index = allUsersSnap.firstIndex { $0.key == thisUsersUid } else {
print("no user: \(thisUsersUid) found")
return
}
let thisUserSnap = allUsersSnap[index] //keep this so it can be compared later
allUsersSnap.remove(at: index)
let thisUsersAnswer = thisUserSnap.childSnapshot("answer").value as? String ?? "No Answer"
for otherUserSnap in allUsersSnap {
let otherUsersAnswer = otherUserSnap.childSnapshot("answer").value as? String ?? "No Answer"
if orherUsersAnswer == thisUsersAnswer {
//do something because the answers match
}
}
})