app crash when success initialize data MVVM - ios

Question

my apps crash when I try to passing the data into another controller but it was successfully load data in my viewController. it's kinda weird though because the data successfully display in my label and my imageView in my controller, what can I suspect is the data is not yet being load. but if the data not being load why the imageView display my data, here I show you my code.
// This is my schoolListViewModel
class SchoolListViewModel {
private(set) var schoolListViewModel = [SchoolViewModel]()
private let services: ProfileServices
private let schools = UserDefaults.getSelectedSchool()
var count: Int {
return schoolListViewModel.count
}
var id: String {
selectedSchoolID()
}
var imageUrl: String {
selectedSchoolImageURL()
}
var schoolName: String {
selectedSchoolName()
}
var schoolCity: String {
selectedSchoolCity()
}
init(services: ProfileServices) {
self.services = services
}
}
extension SchoolListViewModel {
func loadData(success: #escaping (() -> Void), failure: #escaping ((String) -> Void)) {
services.fetchSchoolList { [weak self] result in
switch result {
case .success(let schools):
self?.schoolListViewModel = schools.compactMap({ SchoolViewModel(school: $0)
})
success()
case .failure(let error):
failure(error.localizedDescription)
}
}
}
}
// this is in my profileViewController
var schoolListViewModel: SchoolListViewModel!
private let profileServices = ProfileServices()
// this is my viewModel in my viewDidLoad
progressHUD.show(in: self.view)
schoolListViewModel = SchoolListViewModel(services: profileServices)
schoolListViewModel.loadData(success: {
self.progressHUD.dismiss(animated: true)
self.populateSchool()
}) { [weak self] error in
self?.showHUDWithError(error)
}
schoolSelectionBtn.addTarget(self, action: #selector(handlePickSchool), for: .touchUpInside)
// This is my objc function
private func showHUDWithError(_ error: String) {
progressHUD.textLabel.text = "Error"
progressHUD.detailTextLabel.text = error
progressHUD.dismiss(afterDelay: 4)
}
#objc private func handlePickSchool() {
let selectSchoolVC = SelectSchoolPopUpVC()
selectSchoolVC.schoolListViewModel = schoolListViewModel
present(selectSchoolVC, animated: true, completion: nil)
}
// this is in my SchoolPopUpVC controller
var schoolListViewModel: SchoolListViewModel!
// this is where the error goes in my schoolPopUpVC tableViewDataSource
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return schoolListViewModel.count
}
this where when I try to passing the data, the error show in my tableView numberOfRowsInSection
unexpected found nil when try to unwrapping optional value

Answer 1

You are using an implicitly unwrapped optional for schoolListViewModel but you don't assign a value until viewDidLoad executes. As it's name implies, that method executes after the view is loaded. You refer to schoolListViewModel in numberOfRowsInSection which will be called after the view is loaded but before viewDidLoad has executed, so you get a crash.
The simple fix is to conditionally unwrap schoolListViewModel in that method:
return schoolListViewModel?.count ?? 0