Swift 3 Variable self-removes - swift3

Question

I have very-very strange things.
In my simple function I create variable which contains dictionary of settings parameters. It is set as 'let', so inner loop just reads it.
In a random moment of loop time it crashes with "unresolved settings".
It seems like smth makes it nil. Who does it?
private static func preferencesFilter(userIDs: [Int], access: String) -> [User] {
self.sharedInstance.delegate?.updateActionLabel(label: "Filter")
var result = [VKUser]()
let settings = self.parseSettings()
let progressFraction = 1.00 / Float(userIDs.count)
var n = 0
for userID in userIDs {
if sharedInstance.stopped {
return []
}
n += 1
let user = VKUser.getUser(id: userID, access_token: access_token)
if settings["gender"] != nil {
if user.sex == settings["gender"] as! String {
if (user.born?.isBetweeen(date1: settings["minAge"] as! Date, date2: settings["maxAge"] as! Date))! {
if settings["country"] != nil {
if user.country == settings["country"] as! String {
result.append(user)
}
}
else {
result.append(user)
}
}
}
}
else {
if (user.born?.isBetweeen(date1: settings["minAge"] as! Date, date2: settings["maxAge"] as! Date))! {
if settings["country"] != nil {
if user.country == settings["country"] as! String {
result.append(user)
}
}
else {
result.append(user)
}
}
}
self.sharedInstance.delegate?.updateProgress(value: Float(n) * progressFraction)
}
return result
}

Answer 1

I refactored your code into something more swift like:
private static func preferencesFilter(userIDs: [Int], access_token: String) -> [User]? {
guard userIDs.count > 0 else {
return [User]() // no input, return empty list
}
let settings = self.parseSettings()
guard let minAge = settings["minAge"] as? Date,
let maxAge = settings["maxAge"] as? Date
else {
return nil
}
let country = settings["country"] as? String // specified or nil
let gender = settings["gender"] as? String // specified or nil
sharedInstance.delegate?.updateActionLabel(label: "Filter")
var result = [VKUser]()
let progressFraction = 1.00 / Float(userIDs.count)
var n = 0
for userID in userIDs {
if !sharedInstance.stopped {
n += 1
let user = VKUser.getUser(id: userID, access_token: access_token)
var shouldInclude = true
if user.sex != gender { // wrong sex or no required gender specified
shouldInclude = false
}
if user.country != country { // wrong country or no required country specified
shouldInclude = false
}
if let born = user.born {
if !born.isBetweeen(date1: minAge, date2: maxAge) {
shouldInclude = false
}
} else { // no user.born date, cant check if in range
shouldInclude = false
}
if shouldInclude {
result.append(user)
}
sharedInstance.delegate?.updateProgress(value: Float(n) * progressFraction)
}
}
return result
}
Is that what you intended to write? How is that running for you?
Can you change this into a non-static method? Makes more sense to me.
You can see it returns an optional now, since the method might fail with a nil. Your calling code should handle that correctly.