How to save variable when leaving view

Question

In my main view, I am collecting data from two other views. I start in the main view, go to the next view to get the data and go back to the original view. Then I go to the last view and get more data, but when I go back the original data is gone. How do I save it before leaving?

I have tried using viewWillDisappear but it wasn't working. Is this a good approach and if so, how do I go about using it?

These are the two pieces of data coming in via segue:

var homeTeamName = String ()
var awayTeamName = String ()

I do this when I load:

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.    }
    HomeName.text = homeTeamName
    HomeImage.image = UIImage(named:homeTeamName)
    AwayName.text = awayTeamName
    AwayImage.image = UIImage(named:awayTeamName)

}

Note: Everything with away is coming from one view, and everything with home is coming from another.

Now I am storing like this:

override func viewWillDisappear(_ animated: Bool) {
    UserDefaults.standard.set("value", forKey: "homeTeamName")
}

Retrieving like this:

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.    
    UserDefaults.standard.string(forKey: "homeTeamName")
}

Still not working.

Thanks in advance!

You can use appdelegate for the same you can check my previous ans here https://stackoverflow.com/questions/45407423/sharing-data-between-multiple-view-controllers-without-segue-swift-3/45408261#45408261. — luckyShubhra, Aug 12 '17 at 04:02
Not really I changed the layout so that the views were on one and I just segue the data. All works good, but not with any of these solutions. — Stefan Walzer-Goldfeld, Aug 12 '17 at 16:15

Aditya Srivastava · Accepted Answer · 2017-08-12T04:23:41.823

0

You cannot the store variable in the ViewController class when you leave it. Everything probably gets destroyed. As you have to store just two strings, the best way to do is to use UserDefaults.

Storing

UserDefaults.standard.set("value", forKey: "homeTeamName")

Retrieving

UserDefaults.standard.string(forKey: "homeTeamName")

Use this for printing log

print("printingValue\(UserDefaults.standard.string(forKey: "homeTeamName"))")

Hope it Helps!

edited Aug 12 '17 at 04:23

answered Aug 12 '17 at 03:12

Aditya Srivastava

2,630
2
13
23

At what point do I run these lines of code? Would I store in viewWillDisappear and then retrieve at view did load? Also, I will be having up to 20 more strings I want to store. Should I still use the same method? – Stefan Walzer-Goldfeld Aug 12 '17 at 03:16
Yes you have to store in viewWillDisappear and retrieve at viewDidLoad. Moreover you can store many strings in UserDefaults. You can make a separate class for this purpose or in whichever way you want – Aditya Srivastava Aug 12 '17 at 03:27
Edited original post. I this what you mean? – Stefan Walzer-Goldfeld Aug 12 '17 at 03:34
It will surely print the string "value" in viewDidLoad(). You can log it by using print("printingValue\(UserDefaults.standard.string(forKey: "homeTeamName"))") – Aditya Srivastava Aug 12 '17 at 03:38
Have you printed it? – Aditya Srivastava Aug 12 '17 at 03:51
It still isn't working. I believe it is storing the value but I am accessing it at the wrong time, or something. I really have no idea what is happening. I tried that line but it gave me an error. – Stefan Walzer-Goldfeld Aug 12 '17 at 03:59
Can you please tell me the value what it's printing in viewDidLoad ? So please let me know what is the error – Aditya Srivastava Aug 12 '17 at 04:02
It says Incorrect argument label in call (have 'forKey:', expected 'forKey:') and expected ',' separator. The build crashes. – Stefan Walzer-Goldfeld Aug 12 '17 at 04:06
Please attach the method where you were getting this error – Aditya Srivastava Aug 12 '17 at 04:11
WHen I run your line to print it: print("printingValue(UserDefaults.standard.string(forKey‌: "homeTeamName"))") – Stefan Walzer-Goldfeld Aug 12 '17 at 04:19
Please Check my edited answer and use that line of code to print. It surely work like charm – Aditya Srivastava Aug 12 '17 at 04:24
Not working. It is putting everything but homeTeamName in commas. Is that the goal? – Stefan Walzer-Goldfeld Aug 12 '17 at 04:29
`UserDefaults` is not the proper way to pass data between view controllers. Please read https://stackoverflow.com/questions/5210535/passing-data-between-view-controllers – vadian Aug 12 '17 at 04:30
String will be always printed in inverted commas. That's the syntax of it – Aditya Srivastava Aug 12 '17 at 04:30
@vadian I'm not passing data, I just want to be in the view controller when I go to another one and then come back. – Stefan Walzer-Goldfeld Aug 12 '17 at 04:37
@AdityaSrivastava Still having the error not sure I understand the goal of the line of code. – Stefan Walzer-Goldfeld Aug 12 '17 at 04:37
*go to the next view to get the data and go back* actually means *passing data between controllers* ;-) – vadian Aug 12 '17 at 04:41
Just retrieve and save it in a variable. For Eg : - homeTeamName = UserDefaults.standard.string(forKey: "homeTeamName") . I don't know where is the problem, it's really easy stuff – Aditya Srivastava Aug 12 '17 at 04:42

score 0 · Answer 2 · answered Aug 12 '17 at 04:11

0

hey write this for data storing

override func viewWillDisappear(_ animated: Bool) {
    let userDefault = UserDefaults.standard
    userDefault.set("value", forKey: "homeTeamName")
}

and Write this for Data Retriving Write this

override func viewWillAppear(_ animated: Bool) {
    let userDefault = UserDefaults.standard
    userDefault.value(forKey: "homeTeamName")
}

i think it helps u.

answered Aug 12 '17 at 04:11

Mitul.Patel

252
2
8

what is .standard? – Stefan Walzer-Goldfeld Aug 12 '17 at 04:18
it is preference dictionary which saves data and it will delete when u uninstall application. Userdefaults.standard is preference dictionary. and userdefault is object. and write that code into viewwilldisappear and viewwillappear – Mitul.Patel Aug 12 '17 at 04:20
I think I found my problem. When I retrieve with in the viewWillAppear, do I need to do this: homeTeamName = userDefault.value(forKey: "homeTeamName") – Stefan Walzer-Goldfeld Aug 12 '17 at 04:22
yea that is problem and always create object of Prefrance so it is better for Programming. – Mitul.Patel Aug 12 '17 at 04:24
also, if the userdefault is set the first time it leaves the view, will it change to the new value of homeTeamName when it leaves a second time? – Stefan Walzer-Goldfeld Aug 12 '17 at 04:27
it replace with the the second value. – Mitul.Patel Aug 12 '17 at 04:29
I don't know how to explain my problem. The view loads and the homeTeamName is blank. I leave to view 2 and when I come back the name has been segued to the original view and works fine. Then I go to view 3 and it disappears. I don't know if this knowledge changes the logic or maybe I have very little understanding of what I'm doing but it isn't working. – Stefan Walzer-Goldfeld Aug 12 '17 at 04:35
u can any were access user default. which place u need that value u can create a userdefault object and write that code for retraving u can get that value easily. – Mitul.Patel Aug 12 '17 at 04:39
Ackkkk This is beyond my knowledge I'm sorry I don't understand. THanks for the help though. I apreciate it – Stefan Walzer-Goldfeld Aug 12 '17 at 04:43

How to save variable when leaving view

2 Answers2