What is the simplest way to modify variable by using the Button for later use of that variable in another View Controller? - swift

Question

I have two view controllers. One VC with a button and a label and one VC only with a label. I created button action that can modify variable (declared in the class of that first viewcontroller) if the button is pressed and I can show that MODIFIED variable as the label in that same VC but my intent is to show that MODIFIED variable on another VC.
I want to use that button to go to the second VC where the modified variable should be displayed on the label when that VC is displayed. In first VC I declared:
var myVariable: String = "default"
In the button action:
{myVariable = "700"}
In second VC I declared:
let vc1: ViewController1 = ViewController1()
I assigned an action to the button in first VC (dragging to second VC to show the second VC) and in viewdidload of the second VC I try to acces the variable from first VC with:
label.text = vc1.myVariable and it accesses it but ...
...but the result is DECLARED/notMODIFIED state of variable. So if I show myVariable on same VC it is OK but on the second VC myVariable was not changed by the button action on the first VC.
I am trying to avoid delegation as it seems complicated..
What is the easiest way to accomplish task? Thank you guys.

Answer 1

To get updated value of first VC variable to second VC you can use NSNotificationCenter.
In first VC when you change value at that time you have to post notification with dictionary like following.
NotificationCenter.default.post(name: NSNotification.Name("ValueUpdate"), object: nil, userInfo: ["variable": myVariable])
For that you have to observe Notification in second VC
NotificationCenter.default.addObserver(self, selector: #selector(handleNotification(notification:)), name: Notification.Name("ValueUpdate"), object: nil)
And then you have to implement following method to get update in your second VC
#objc func handleNotification(notification: Notification) {
label.text = notification.userInfo?["variable"]
}

Answer 2

The SIMPLEST way to do this is to define a global variable. So you can access it from anywhere. It should be define outside of anything to be global.
#import UIKit
var myGlobalVariable = "Initial value"
class MyClass { ... }
then you can change or read it from anywhere like print(myGlobalVariable).
Note that although it is the simplest solution, it is also THE WORST solution too. Global functions and variables use cases are vary rare.

Answer 3

Inject your data via initializer while showing controller.
show(SecondViewController(name: name), sender: nil)
Check out this code.

Answer 4

#Eljer...
Although Delegation seems VERY hard at first its very easy.
You need to remember 3 steps only as a beginner ! I'll try to make it easy for you to use here.
Step 1 : Create tempVariable (of same type) on second View controller also (you can make with same name also doesnt matter)
Step 2 : Write this code:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let xyz = segue.destination as! abc
}
The xyz is the name you want to call it with.
The abc is the name of your second view controller where you made the other same type of variable.
What this will do is, it will make an object of EVERYTHING (that includes all variables and functions) that you have on your Second View controller available to you on your First view controller also.
To use / assign value to the label on second view controller what you need to do is...
just add :
xyz.yourVariableNameOnSecondViewController = variableNameOnFirstViewController
this will assign the value of your variable on First VC to the variable on Second VC also
Finally, to get the value updated. You need to get this updated value using viewDidLoad on your second view controller.
I hope this helps, if its still confusing ask me anything.
Gluck