gistfile1.txt

//
// Not sure how to return "data" from getTrailWarnings...
//
func getTrailWarnings() -> Array<Dictionary<String, AnyObject>>? {
    let serviceUrl = "http://www.example.com/json"
    guard let url = NSURL(string: serviceUrl) else { return nil }

    requestTrailWarnings(url) { (data: Array<Dictionary<String, AnyObject>>?) in
        return data
    }
}

private func requestTrailWarnings(url: NSURL, completion: (Array<Dictionary<String, AnyObject>>?) -> Void) -> Void {
    let request = NSMutableURLRequest(URL: url)
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: {
        (data, response, error) in
        
        UIApplication.sharedApplication().networkActivityIndicatorVisible = false
        
        if error == nil {
            if let data = data {
                do {
                    if let json = try NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves) as? NSDictionary {
                        
                        guard let features = json["features"] as? NSArray else { return }
                        guard features.count > 0 else { return }
                        
                        var warnings = [Dictionary<String, AnyObject>]()
                        
                        for feature in features {
                            if let feature = feature as? NSDictionary,
                                let attributes = feature["attributes"] as? NSDictionary,
                                let geometry = feature["geometry"] as? NSDictionary {
                                if let trailName = attributes["Name_Trail"] as? NSString where geometry.count == 2 {
                                    let warning: Dictionary = [
                                        "trailName": trailName,
                                        "geometry": geometry
                                    ]
                                    warnings.append(warning)
                                }
                            }
                        }

                        // return warnings to caller
                        completion(warnings)
                    }
                } catch {
                    
                }
            }
        }
    })
    
    UIApplication.sharedApplication().networkActivityIndicatorVisible = true
    task.resume()
}