Since I upgraded to Xcode 11 and Swift 5.1 I've encountered a strange issue -- after an optional variable is instantiated, it can still show as up nil in the Xcode debugger!
I have an optional class variable called booking:
var booking: Booking?
It's of type Booking:
public struct Booking: Codable {
var id: Int?
var start_time: Date?
var payment_currency: String = "USD"
var payment_amount: Int?
}
When I'm stepping through the code, I can see booking before it's allocated... It's nil, great:
Then after it's allocated... What, still nil??:
I wondered if it was being treated like a lazy variable somehow. But it's not really nil, because it can be accessed:
After searching for a while, I wondered if my build schema in Xcode didn't have its "Debug executable" flag set. But it does. I even cleaned and rebuilt the project with the flag off and on to be sure.
Whether I view booking in the Variables View or enter p booking in the Console View, it shows up as nil.
What's going on here? I need the predictability of debugging I had before this upgrade.
UPDATE
I distilled a simple way to reproduce the issue. First, create an empty single-view project and add this to the top of AppDelegate.swift:
public struct Booking: Codable {
var start_time: Date?
var payment_currency: String = "USD"
}
Then add these lines to the application(_:didFinishLaunchingWithOptions:) func:
booking = Booking()
print("booking.payment_currency = \(booking?.payment_currency ?? "NULL")")
Set a breakpoint as before and when running, notice that the debugger shows booking as nil even after being assigned, as in my original case.
Then comment out the start_time variable, re-run, and notice that now the debugger shows booking having a value after being assigned, as one would expect.
So it seems that Date variables, optional or not, in a struct like this make debugging confusing. Specifically Date variables -- change the variable to other types like Int, Int?, String, String?... and there's no issue.
Unless I'm missing something very basic, this seems like a bug in the Xcode debugger to me. If so, would the best way to report it be at https://developer.apple.com/bug-reporting/?
