Guard Statements in Initializer fail to initialize all values

Question

I followed this course after 2.0 came out so instead of using if let I used guard statements just to practice doing so. Im familiar with them, use them all the time and know the proper syntax. However I was pulling my hair out because there was one error at the bottom of my initializer: "return from initializer without initializing all stored properties".

I even set the values to nil in the else part of the guard just in case, but it still wouldn't compile. I quadruple checked multiple times that I had everything set. The only difference in code was my use of guard statements. Is this a known issue?

struct DailyWeather {

    let maxTemp: Int?
    let minTemp: Int?
    let humidity: Int?
    let precipChance: Int?
    var summary: String?
    var icon: UIImage? = UIImage(named: "default.png")
    var largeIcon: UIImage? = UIImage(named: "default_large.png")
    var sunriseTime: String?
    var sunsetTime: String?
    var day: String?

    let dateFormatter = NSDateFormatter()

    init(dailyWeatherDictionary: [String:AnyObject]) {

        minTemp = dailyWeatherDictionary["temperatureMin"] as? Int
        maxTemp = dailyWeatherDictionary["temperatureMax"] as? Int
        guard let humidityFloat = dailyWeatherDictionary["humidity"] as? Double else { humidity = nil ; return }
        humidity = Int(humidityFloat * 100)
        guard let precipFloat = dailyWeatherDictionary["precipProbability"] as? Double else { precipChance = nil ; return }
        precipChance = Int(precipFloat * 100)
        summary = dailyWeatherDictionary["summary"] as? String
        guard let
            iconString = dailyWeatherDictionary["icon"] as? String,
            iconEnum = Icon(rawValue: iconString) else { icon = nil ; largeIcon = nil ; return }
        (icon, largeIcon) = iconEnum.toImage()

        guard let sunriseDate = dailyWeatherDictionary["sunriseTime"] as? Double else { sunriseTime = nil ; return }
        sunriseTime = timeStringFromUnixTime(sunriseDate)
        guard let sunsetDate = dailyWeatherDictionary["sunsetTime"] as? Double else { sunsetTime = nil ; return }
        sunsetTime = timeStringFromUnixTime(sunsetDate)
        guard let time = dailyWeatherDictionary["time"] as? Double else { day = nil ; return }
        day = dayStringFromUnixTime(time)

    }
    (methods follow)

Answer 1 · 2016-02-14T05:55:34Z

February 14, 2016 5:55am

All properties have to be initialized before any guard statementreturns. Thus, you make sure that every property is initialized before theelsestatement of anyguardstatement finishes. A perhaps faster and easier solution would be to make the initializer itself fail if any of theguardstatements do. You can do this by making theinitreturn an Optional, andreturn nilin theguard`s where something goes wrong, like this:

init(dailyWeatherDictionary: [String: AnyObject])?{
  //Initialize stuff
  guard someProperty = dailyWeatherDictionary["someKey"] else{ return nil }
  // Initialize more stuff, in case the above guard succeeds
  //Repeat as necessary
}

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Reed Carson

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Guard Statements in Initializer fail to initialize all values

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Michael Hulet

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