Can't unwrap 'Optional.None'

Question

When confronting the error fatal error:

Can\'t unwrap Optional.None

It is not that easy to trace this. What causes this error?

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Answer 1

You get this error, because you try to access a optional variable, which has no value. Example:

// This String is an optional, which is created as nil.
var optional: String?

var myString = optional! // Error. Optional.None

optional = "Value"
if optional {
    var myString = optional! // Safe to unwrap.
}

You can read more about optionals in the official Swift language guide.