Setting DarkTheme has no effect Braintree iOS v4 SDK - swift

Question

The documentation clearly says it can be done, easy breezy:
https://developers.braintreepayments.com/guides/drop-in/customization/ios/v4#themes
I can indeed customize the primaryTextColor to red.
Here is a screenshot, that demonstrates that red works but not darkTheme:
And is here is my code in my UIViewController:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
showDropIn(clientTokenOrTokenizationKey: clientToken)
}
func showDropIn(clientTokenOrTokenizationKey: String) {
BTUIKAppearance.darkTheme()
BTUIKAppearance.sharedInstance().primaryTextColor = UIColor.red
let request = BTDropInRequest()
request.vaultManager = true
let dropIn = BTDropInController(authorization: clientTokenOrTokenizationKey, request: request)
{ (controller, result, error) in
if (error != nil) {
print("ERROR")
} else if (result?.isCancelled == true) {
print("CANCELLED")
} else if let result = result {
// Use the BTDropInResult properties to update your UI
// result.paymentOptionType
// result.paymentMethod
// result.paymentIcon
// result.paymentDescription
}
controller.dismiss(animated: true, completion: nil)
}
self.present(dropIn!, animated: true, completion: nil)
}

Answer 1

So Braintree's documentation on Theme's is a bit poorly choose wording IMO.
The instruction is what is misleading to me: "To use the Dark theme instead, call this method before initializing Drop-in". Yet you have to initialize or instantiate the drop-in before setting darkTheme.
The instruction might better read: "To use the Dark theme instead, call this method before presenting the Drop-in"
Here is my working code:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
showDropIn(clientTokenOrTokenizationKey: clientToken)
}
func showDropIn(clientTokenOrTokenizationKey: String) {
let request = BTDropInRequest()
request.vaultManager = true
dropIn = BTDropInController(authorization: clientTokenOrTokenizationKey, request: request)
{ (controller, result, error) in
if (error != nil) {
print("ERROR")
} else if (result?.isCancelled == true) {
print("CANCELLED")
} else if let result = result {
// Use the BTDropInResult properties to update your UI
// result.paymentOptionType
// result.paymentMethod
// result.paymentIcon
// result.paymentDescription
}
controller.dismiss(animated: true, completion: nil)
}
BTUIKAppearance.darkTheme()
BTUIKAppearance.sharedInstance()?.primaryTextColor = UIColor.lightGray
self.present(dropIn!, animated: true, completion: nil)
}