How does one change the value of a global variable in a function to be used later on?

Question

I am trying to create a weather application, and in order to do that I need to parse out JSON. This works, (which I know because I tested it by printing), but I cannot change the value of the data I get to an already initialized global variable. A similar question was asked before, but even using the provided answers, I was not able to solve my own problem.

The following lines are where I initialize my global variables:

var currentTemperature = 88
var currentTime = 789

And the following Lines are where I parse the JSON and test by printing in my viewDidLoad function:

let url = URL(string: "https://api.darksky.net/forecast/c269e5928cbdadde5e9d4040a5bd4833/42.1784,-87.9979")

    let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in

        if error != nil {
            print("error")
        }
        else {

            if let content = data {

                do {

                    let json = try JSONSerialization.jsonObject(with: content, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject

                    if let jsonCurrently = json["currently"] as? NSDictionary {

                        if let jsonCurrentTime = jsonCurrently["time"] {

                            currentTime = jsonCurrentTime as! Int
                            print(currentTime)

                        }

                        if let jsonCurrentTemperature = jsonCurrently["temperature"] {

                            currentTemperature = jsonCurrentTemperature as! Int
                            print(currentTemperature)


                        }



                    }

                } catch {

                }

            }

        }

    }

    task.resume()

I use the global variables when setting the text of a label in a different class: (however, only the initial value I set to the variable shows up, not the one from the parsed JSON)

let currentTemperatureLabel: UILabel = {
    //label of the current temperature
    let label = UILabel()
    label.text = String(currentTemperature) + "°"
    label.textColor = UIColor(red: 150/255, green: 15/255, blue: 15/255, alpha: 0.8)
    label.textAlignment = NSTextAlignment.center
    label.font = UIFont(name: "Damascus", size: 130)
    label.font = UIFont.systemFont(ofSize: 130, weight: UIFontWeightLight)
    return label
}()

The JSON example request can be found here: https://darksky.net/dev/docs#api-request-types

No matter what I do, I am not able to use the data from the JSON when I attempt to access the two global variables mentioned before.

Answer 1

var currentTemperature : Double = 88
var currentTime = 789

//...

override func viewDidLoad() {
    super.viewDidLoad()

    let url = URL(string: "https://api.darksky.net/forecast/c269e5928cbdadde5e9d4040a5bd4833/42.1784,-87.9979")

    let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in

        if error != nil {
            print("error")
        }
        else {

            if let content = data {

                do {

                    let json = try JSONSerialization.jsonObject(with: content, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject

                    if let jsonCurrently = json["currently"] as? NSDictionary {

                        if let jsonCurrentTime = jsonCurrently["time"] as? Int {

                            currentTime = jsonCurrentTime
                            print(currentTime)

                        }

                        if let jsonCurrentTemperature = jsonCurrently["temperature"] as? Double {

                            currentTemperature = jsonCurrentTemperature
                            print(currentTemperature)


                        }



                    }

                } catch {

                }

            }

        }

    }

    task.resume()
}

I did these edits above to your code:

• Changed your currentTemperature to be Double (Look at your JSON response to see what kind of response you get and what kind of data type it can be)
• When trying to get "time" and "temperature" added optional wrapping to get the data correctly from the response with correct data type so that when assigning to your variables you wont need to do explicit unwrapping

EDIT: Updated answer based on your comment about the global variables not being part of the class