Pass array to another View Controller

Question

I have Tab Bar Controller, where I have few view controllers, but I want to pass array of values (workoutNames) to another view in my Tab Bar Controller. I wonder what's best option to do this and I've decided to use way of passing data with property. But when I try to retrieve data I get empty array. I could also use firestore to retrieve data in my Second View Controller, but It lasts too long, so I decided to passing data between views than retrieve data from firestore every time.

First View Controller

class HomeTableViewController: UIViewController

// I need to pass this array to another view
    var workoutsName: [String] = [] 

...
      func sendDataToCalendar() {
      // IN THIS FUNCTION I RETRIEVE DATA FROM FIRESTORE AND UPDATE ARRAY WITH VALUES
// After all I print this array to check if everything is correct, and my data is here
print("\(workoutsName)")

    }

Here is my Second View Controller when I want to use array from First View Controller

   class CalendarViewController: UIViewController {
    var arrayOfTitles = [String]()
    .
    .
    .
    func getArrayFromHome() {
    let homeVC = HomeTableViewController()
    homeVC.workoutsName = arrayOfTitles
    // NOW I PRINT TO CHECK IF DATA EXISTS
    print("\(arrayofTitles)"
    }

And its empty, so data didn't pass.

Maybe it's not the best way to pass data, but main idea of this is that I will need to use this array in few view controllers. These controllers won't be connected by segue, so I can't use prepareforSegue. It's not one to one relationship (in future I will need this array in few controllers), so I shouldn't use delegate. I don't think that notification will be ok too, so I think that it's best option to pass data by property. But maybe I am wrong, so please correct me.

Answer 1

In your getArrayFromHome() function you are not accessing HomeTableViewController instance where you got the data but creating a new instance. That's why the array is empty. You end up with 2 instances of HomeTableViewController, one in use with the correct array and the dummy one created in the function with an empty array.

Would be better if you pass the data in the same place where you have a reference to CalendarViewController.

Let's say that you are creating and presenting CalendarViewController in your HomeTableViewController like:

let calendarViewController = CalendarViewController()
calendarViewController.arrayOfTitles = workoutNames
// Here is the presentation or push of calendarViewController

It will be useful for you to read this SO question

Answer 2

The reason why it doesn't work is that you instantiate a new HomeTableViewController with empty data.

If this data will be used on lots of place, why not save it locally? user default seems like it fit your needs.

func sendDataToCalendar() {
    UserDefaults.standard.set(workoutsName, forKey: "workoutsName")
}

Then you can read it later on

func getWorkoutNameArray() {
    let workoutName = UserDefaults.standard.object(forKey: "workoutsName") as? [String]

}