I'm trying to essentially do an valid check on a String in Swift, however I'm getting an error Conditional downcast from 'String' to 'String' always succeeds.
zipCode is created:
var zipCode = String()
Checking for a valid string at a later time:
if let code = zipCode as? String {
println("valid")
}
Can someone help me understand what I'm doing wrong?
If zipCode can be "unset", then you need to declare it as an optional:
var zipCode: String?
This syntax (which is known as optional binding):
if let code = zipCode {
print("valid")
// use code here
}
is used for checking if an optional variable has a value, or if it is still unset (nil). If zipCode is set, then code will be a constant of type String that you can use to safely access the contents of zipCode inside the if block.
String! is an implicitly unwrapped optional, you probably meant String? ? - And the conditional cast as? String it not necessary here and causes a compiler error if the variable is known to be a (optional) string.
zipCodeis a kind ofStringin every moment, why do you want to downcast it toString, if you already know it is aString? the compiler has been just intelligent enough to warn you not to do such pointless task. if you want to work optional, that would make sense, but your OP has not mentioned anything about any optionals.