Passing Self ViewController as a Parameter? - ios

Question

I have a TableView inside my app and i populate it from a JSON, which is downloaded inside a DataService class. This DataService class simply does the download & save data to array operation.
Inside my ViewController class, i also have an array for this data that is initialized empty at the beginning, filled with the data from DataService afterwards. Since i need to fill the data array (the one inside ViewController class) once the download operation is completed, DataService class needs to reach this array. So i decided to pass the ViewController object itself to DataService class so that it can fill VC's array with downloaded data and also reload its tableView data.
So my DataService class looks like this:
var dataArray: [EtkinlikCellData] = []
func fetchData(senderVC: EtkinliklerVC) {
// Download & fill dataArray operations
senderVC.dataArray = self.dataArray // setting sender VC's array
senderVC.tableView.reloadData() // reloading sender VC's table data
}
And how's it used inside ViewController class:
var dataArray = [EtkinlikCellData]()
override func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
DataService.instance.fetchData(senderVC: self)
}
I know that if i did the fetch operation directly inside the ViewController class, there would be no problems since fetchData() method would reach the dataArray and tableView object itself. But since it is in another class, would it be wrong or harmful to pass a ViewController object as a parameter? Thanks.

Answer 1

The only threat is retain cycles and you can avoid it with weakly reference the object like
Option 1: // problem model shouldn't have any UI content
weak var delgate:EtkinliklerVC?
fetchData(senderVC: EtkinliklerVC) {
self.delegate = senderVC
....
self.delegate?.dataArray = self.dataArray
self.delegate?.tableView.reloadData()
Option 2 :
Establish a completion ( Recommended )
func fetchData(completion:#escaping:([String] -> ())) {
completion(arr)
}
then use it
DataService.instance.fetchData() { [weak self] arr in
// set it and reload
}
Plus:
Say you left your current code as it's , since the singleton alive which means it's strongly retained and you pass the vc object to it , user opens the vc and before data returns he pressed back button in your vc , since there is no weak reference between the singleton and the vc , then the vc will still be in memory while it should be de allocated