Weather.swift

enum WeatherValue<Value> {
    case single(value: Value)
    case minmax(min: Value, max: Value)
}

struct WeatherFeature<T> {
    let unit: String
    let value: WeatherValue<T>
}

struct DayNightWeather {
    let windSpeed: WeatherFeature<Double>
    let windDirection: String
    let precipitationProbability: Int
    let phrase: String
    let icon: Int
}

// Since Swift 3.1 there's a neat feature called "Type nesting with generics" is
// around, however implementation is buggy and leads to runtime error
// https://bugs.swift.org/browse/SR-4383
// As a workaround, WeatherValue, WeatherFeature, DayNightWeather are standalone types
struct Weather {
    let effectiveDate: Date
    let temperature: WeatherFeature<Double>
    let realFeel: WeatherFeature<Double>
    let day: DayNightWeather
    let night: DayNightWeather
}