The problem is that you need to return SOMETHING from getForecast -- right now
you're returning nothing.
The task will execute at some point "in the future" after the routine ends. An
"easy" solution is to pass a closure to getForecast that will take a
Dictionary? as a parameter (just in case there's an error, make the parameter
an optional). Your task then calls that closure with the resulting Dictionary.
Welcome to asynchronous programming!
--
Glenn L. Austin, Computer Wizard and Race Car Driver <><
> On Dec 22, 2015, at 6:25 AM, Eric E. Dolecki <edole...@gmail.com> wrote:
>
> I am trying to return a dictionary from a method that uses a queue. I'm not
> sure how to actually return though as I get an error (can't convert value
> of type '() -> Dictionary<String,String>' to expected argument type
> 'dispatch_block_t'. I've tried a number of things but none prevent an error
> somewhere. I could ditch the queue altogether, but it feels better to use
> one.
>
> - Eric
>
>
> func getForecast(cityName:String) -> Dictionary<String,String> {
> let baseUrl: String = "
> https://urldefense.proofpoint.com/v2/url?u=http-3A__api.openweathermap.org_data_2.5_forecast&d=BQIFaQ&c=Hw-EJUFt2_D9PK5csBJ29kRV40HqSDXWTLPyZ6W8u84&r=GBXZhacxqultU1tKBDt744IExU5-txpVlucNMcizFfQ&m=tP_xkrFwAs-9Qn22yQLRdAJiwAh5yxUlmqG-ZbklzuE&s=W-iZmEs7W3Hf-MPt3D4_XkNcpy9J8LIp8HXEjh7aL1o&e=
> "
> let url: String =
> "\(baseUrl)?q=\(theCityName)&units=imperial&appid=\(APIKey)"
> let finalUrl: NSURL = NSURL(string: url)!
> let session = NSURLSession.sharedSession()
> let task = session.dataTaskWithURL(finalUrl, completionHandler:
> {data, response, error -> Void in
> if error != nil{
> print(error!.localizedDescription)
> }
> var err: NSError?
> let qualityOfServiceClass = QOS_CLASS_BACKGROUND
> let backgroundQueue =
> dispatch_get_global_queue(qualityOfServiceClass, 0)
> dispatch_async(backgroundQueue, {
>
> let json = JSON(data: data!, options:
> NSJSONReadingOptions(), error: &err)
> //print("response is \(json)")
> let weatherCurrent = json["list"][0]["main"]["temp"]
> let weatherHigh = json["list"][0]["main"]["temp_max"]
> let weatherLow = json["list"][0]["main"]["temp_min"]
> let conditionForecast =
> json["list"][0]["weather"][0]["description"].stringValue
>
> * dispatch_async(dispatch_get_main_queue(), { () ->
> Dictionary<String,String> in*
> * print("Forecast: Current: \(weatherCurrent)ºF.
> H:\(weatherHigh), L:\(weatherLow). Cond:
> \(conditionForecast.capitalizedString).")*
> * let dict = ["current":"\(weatherCurrent)",
> "high":"\(weatherHigh)",*
> * "low":"\(weatherLow)",
> "conditions":"\(conditionForecast.capitalizedString)"]*
> * return dict*
> })
> })
> })
> task.resume()
> }
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