CODEWITHSUNDEEP
swiftoption-typeforced-unwrapping
Danial Kosarifar
Danial Kosarifar

Reputation: 47

Why cant I unwrap this optional value using Swift?

I am trying to get the value for first record which is "2018-05-04 09:00:00 +0000". When I print out `firstRecord', I get an optional value in the terminal:

optional(2018-05-04 09:00:00 +0000).

Then I tried to unwrap it like so: 

if dailyArray.count == 0 {
    print("no record was found")
}else{
    guard let firstRecord : String = dailyArray[0]["startTime"] as! String else {return}
    let firstRecordArray = firstRecord.components(separatedBy: " ")
    print("data exist \(firstRecordArray[0])")
}

And now Xcode is giving me an error saying that you are trying to unwrap a none optional value.

Any idea where am I making a mistake?

Upvotes: 0

Views: 368

Answers (3)

Aron
Aron

Reputation: 3571

You can use optional chaining and the if let syntax to unwrap the variable and make the code much more concise and clear:

// dailyArray should be declared as or typecast to [[String : String]]

guard !dailyArray.isEmpty else {
    print("no record was found")
    exit(1) // or return if in func
}

if let firstRecord = dailyArray.first?["startTime"]?.components(separatedBy: " ") {
    print("data exists: \(firstRecord.first)")
}
else {
    print("no start time date was found")
}

Upvotes: 0

Alexander
Alexander

Reputation: 63137

If you're going to use optional chaining, then you may as well use .first (returns an optional, nil on empty array) rather than [0] (returns value, crashes on empty array):

guard !dailyArray.isEmpty else {
    print("no record was found")
    return
}
guard let firstRecord = dailyArray.first?["startTime"] as? String else {
    return
}
let firstRecordArray = firstRecord.components(separatedBy: " ")
print("data exist \(firstRecordArray[0])")

Upvotes: 0

Abhishek Thapliyal
Abhishek Thapliyal

Reputation: 3708

Do like this

guard !dailyArray.isEmpty, let firstRecord = dailyArray[0]["startTime"] as? String else { return }
let firstRecordArray = firstRecord.components(separatedBy: " ")
print("data exist \(firstRecordArray[0])")

In your code you are typecasting forcely thatswhy

["startTime"] as! String

this means that the value is Strictly string while ? says it can be string

Upvotes: 1

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