How do I check if x is in a variable in classes within a list?

Question

I have a list called mainframe which holds classes. I want to check before adding a new username; if newusername is in mainframe.usernames perform adding the new username in.

pretty much something like this:

import UIKit

class addNewPassword: UIViewController {

    var homeVC = Home()

    @IBOutlet weak var createHolderItem: UITextField!
    @IBOutlet weak var createHolderUsername: UITextField!
    @IBOutlet weak var createHolderPassword: UITextField!



    override func viewDidLoad() {
        super.viewDidLoad()


    }
    @IBAction func savePasswordButton(_ sender: Any) {

        let holder = Holder()
        holder.item = createHolderItem.text!
        holder.username = createHolderUsername.text!
        holder.password = createHolderPassword.text!
    }

  if mainframe.contains(where: { $0.username == holder.username }) {
        print("test")
    }
    else {
            homeVC.mainframe.append(holder)
            homeVC.tableView.reloadData()

            navigationController?.popViewController(animated: true)
    }

}

I pretty much want to run a loop, within an if statement. Or am I approaching it the wrong way?

I'm new to programming, did online tutorials and trying to write my first iOS app for my aunt.

Answer 1

if mainframe.usernames.contains(holder.username) {
...

Answer 2

Use contains :

if mainframe.usernames.contains(holder.username) {
    ...
}