How to show multiple items from Core Data on an MKAnnotation - swift

Question

I am attempting to show multiple objects on my map annotations from Care Data. Currently, I can get title and subtitle to show info with this function
func getData() -> [MKAnnotation]? {
do {
storedLocations = try context.fetch(Fish.fetchRequest())
var annotations = [MKAnnotation]()
for storedLocation in storedLocations {
let newAnnotation = MyAnnotation(coordinate: CLLocationCoordinate2D(latitude: storedLocation.latitude, longitude: storedLocation.longitude))
newAnnotation.coordinate.latitude = storedLocation.latitude
newAnnotation.coordinate.longitude = storedLocation.longitude
newAnnotation.title = storedLocation.species
newAnnotation.subtitle = storedLocation.length
newAnnotation.newTime = storedLocation.time
newAnnotation.newBait = storedLocation.bait
newAnnotation.newNotes = storedLocation.notes
newAnnotation.newWaterTempDepth = storedLocation.water
newAnnotation.newWeatherCond = storedLocation.weather
// print(storedLocation.length)
let newLength = storedLocation.length
let newTime = newAnnotation.newTime
// let newBait = storedLocation.bait
// let newNotes = storedLocation.notes
// let newWaterTempDepth = storedLocation.water
// let newWeatherCond = weatherCond
myLength = newLength!
myTime = newTime!
//
annotations.append(newAnnotation)
}
return annotations
}
catch {
print("Fetching Failed")
}
return nil
}
I am trying to show all of the storedLocation data on the annotation.
By using this extension I found here I am able to add multiple lines to the annotation.
However it is not from the info stored in core data. This is how I set up the func for the extension
func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
guard !(annotation is MKUserLocation) else {
return nil
}
let reuseIdentifier = "pin"
var annotationView = map.dequeueReusableAnnotationView(withIdentifier: reuseIdentifier)
if annotationView == nil {
annotationView = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseIdentifier)
annotationView?.canShowCallout = true
annotationView?.loadCustomLines(customLines: [myLength, myTime])
} else {
annotationView?.annotation = annotation
}
annotationView?.image = UIImage(named: "fish")
return annotationView
Here is the extension.
extension MKAnnotationView {
func loadCustomLines(customLines: [String]) {
let stackView = self.stackView()
for line in customLines {
let label = UILabel()
label.text = line
stackView.addArrangedSubview(label)
}
self.detailCalloutAccessoryView = stackView
}
private func stackView() -> UIStackView {
let stackView = UIStackView()
stackView.axis = .vertical
stackView.distribution = .fillEqually
stackView.alignment = .fill
return stackView
}
}
here is my annotation
import UIKit
import MapKit
class MyAnnotation: NSObject, MKAnnotation {
var coordinate: CLLocationCoordinate2D
var title: String?
var subtitle: String?
var newLength: String?
var newTime: String?
var newBait: String?
var newNotes: String?
var newWaterTempDepth: String?
var newWeatherCond: String?
var detailCalloutAccessoryView: UIStackView?
init(coordinate: CLLocationCoordinate2D){
self.coordinate = coordinate
}
}
When I run I get
this
I am very new to programming and would greatly appreciate any help, and also an explanation of what I am doing wrong Thank you in advance

Answer 1

'!' means Force Unwrapping
myLength = newLength! <- CRASH
As 'newLength' is nil here, you will get a crash on the line where you force unwrap it.
e.g. You can fix the error
myLength = newLength ?? 0
myTime = newTime ?? 0
See also What does "fatal error: unexpectedly found nil while unwrapping an Optional value" mean?