How can a change data based off of user's location? - ios

Question

I created a tableview with 2 cells, with each cell showing both your senators (based off of your location). I used CLGeocoder to successfully grab the user's zipcode, and I then put that value (which is of type string) into a variable that declared outside of the function.
Ideally, I want to go to a different function in the class, and use that string variable (which should hold the user's zip code) to create specific data. However, it doesn't work!
Here is the code that extracts the zip code and puts it in var zipCode:(note that the print function in the if condition successfully prints the zip code in the terminal when I run the program).
let locationManager = CLLocationManager()
var zipcode: String = ""
func getTableInfo() {
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers
locationManager.requestWhenInUseAuthorization()
locationManager.startMonitoringSignificantLocationChanges()
CLGeocoder().reverseGeocodeLocation(locationManager.location!, completionHandler: {(placemarks, error) -> Void in
if error != nil {
print("Reverse geocoder failed with error" + error!.localizedDescription)
}
if placemarks!.count > 0 {
let pm = placemarks![0]
self.zipcode = pm.postalCode!
print(self.zipcode)
}
else {
print("Problem with the data received from geocoder")
}
})
}
I call this function in viewDidLoad() and then in the viewDidLoad() function, using an if-statement, I try to use the zip code to change an array of strings. names[] is declared as a empty array of strings right above the viewDidLoad() function.
if zipcode == "94108" {
names[1] = "WORKS!"
print(names)
}
For some reason, it doesn't print the names! (Note that the zip code is indeed 94108 because 94108 is what prints in the console when I ask to print 'zipcode')

Answer 1

Create a completion handler for your getTableInfo method, like this:
typealias ZipcodeCompletionBlock = (String?) -> Void
func getTableInfo(completionBlock: #escaping ZipcodeCompletionBlock) {
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers
locationManager.requestWhenInUseAuthorization()
locationManager.startMonitoringSignificantLocationChanges()
CLGeocoder().reverseGeocodeLocation(locationManager.location!, completionHandler: {(placemarks, error) -> Void in
if error != nil {
print("Reverse geocoder failed with error" + error!.localizedDescription)
completionBlock(nil)
} else if placemarks!.count > 0 {
let pm = placemarks![0]
self.zipcode = pm.postalCode!
completionBlock(self.zipcode)
} else {
print("Problem with the data received from geocoder")
completionBlock(nil)
}
})
}
Now you can call this function like this inside viewDidLoad:
self.getTableInfo { zipcode in
if zipcode == "94108" {
self.names[1] = "WORKS!"
print(self.names)
}
}

Answer 2

It's probably because of a slight delay in the execution of the code that saves the ZIP code, so zipcode is still "" when your print code is run. Completion handlers are in place because they execute code AFTER the function is done. Put the following code right after print(self.zipcode)
if zipcode == "94108" {
names[1] = "WORKS!"
print(names)
}
Hope that helps!