Hmm, I'm not entirely sure for the Forecast type - I think personally I would keep it an optional like this:

var hourlyWeatherForecast: Forecast<HourWeather>? {

let forecast = (weather?.hourlyForecast) //TODO: handle error case

print("Forecast: \(forecast)")

return forecast

}

And then wherever I'm working with it, include a fall back incase it returns nil:

Text(weatherKitManager.hourlyWeatherForecast?.forecast.first?.temperature.description ?? "error")

But maybe a different resource online might have a better solution? I wish you the best of luck and am excited to see whatever you end up building!