I have my own custom data structures which receive input through the ViewController class. The interface is a simple text field, which is linked to a variable that the contents of the text field is copied to. Upon launching the app, the text field should be prepopulated with data entered in the past. However, as soon as I close the app, the data is lost. I am new to programming and assume this can be remedied by implementing the necessary functions in AppDelegate class, more specifically, under the default applicationWillTerminate function. If this is correct, how do I implement the data saving process? If not, where & how do I make sure data entered is stored so that fields are prepopulated the next time the app is opened?
If you need to store small amount of data, take a look at NSUserDefaults.
If your data better fits to a database, you can use SQLite (may be with a wrapper) or Core Data.
There is also a modern but not yet very mature cross-platform mobile database called Realm (partially open-sourced at the moment).
Since you are saving TextField data(which use mostly small string text) Use NSUserDefaults to store the string for persistence. What you need to do is at textFieldEndEditing save the text to NSUserDefaults and in viewDidLoad assign it to textField.
Saving To NSUserDefaults:
let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject(myTextField.text, forKey: "TextFieldText")
defaults.synchronize()
Retrieving from NSUserDefaults:
let defaults = NSUserDefaults.standardUserDefaults()
if let savedText = defaults.stringForKey("TextFieldText")
{
print("Textfield Text: \(savedText)")
}
Related
I am trying to save boolean in UserDefault in swift.
so when I set value in userDefault, my very next instruction is to switch to view controller and close the current view controller.
so, what is happening now is, sometimes userDefault saves the value in DB, and sometimes it doesn't.
I read documentation from Apple
https://developer.apple.com/documentation/foundation/userdefaults
and found that
At runtime, you use UserDefaults objects to read the defaults that your app uses from a user’s defaults database. UserDefaults caches the information to avoid having to open the user’s defaults database each time you need a default value. When you set a default value, it’s changed synchronously within your process, and asynchronously to persistent storage and other processes.
so, I guess because in the very next line I open a new controller and close the current one so due to which there is inconsistency.
here is my code
func setWalkthroughShown(completionHandler: #escaping ()->()) {
UserDefaults.standard.set(true, forKey: isWalkthroughCompleted)
UserDefaults.standard.synchronize()
completionHandler()
}
I even called UserDefaults.standard.synchronize() so that operation may become synchronous.
even though in the documentation it is clearly written not to use this function.
can someone please guide me where I am wrong? how can I save across all places before closing the current process?
this is the function by which I am retrieving value
func isWalkthroughShown() -> Bool {
return UserDefaults.standard.bool(forKey: isWalkthroughCompleted)
}
here isWalkthroughCompleted is a string and you can see I am using same string for saving and retrieving value
Actually, there was no syntax error in coding.
I was actually testing it in the wrong way.
after submitting for the request of saving data in userdefaults, I was recompiling immediately and as value stores asynchronously so sometimes due to killing of the process I was getting this issue.
thanks to #matt.
for detail iOS UserDefaults falls behind saved content
I’m doing an app to be used as an inventory.
I need to know how to save the state of the stepper
So if I or another user close the app, the state of the stepper won’t change.
My app is targeting multiple users, so if one user has changed the stepper state it will be saved and changed for other users.
The main idea: save UIStepper's value.
It depends on your needs how you should save it:
If you have just one main stepper and this is the whole idea of your
app, you can save value to UserDefaults and then retrieve it
let stepper = UIStepper()
// Saving
UserDefaults.standard.set(stepper.value, forKey: "stepperValue")
// Retrieving
stepper.value = UserDefaults.standard.double(forKey: "stepperValue")
If you have various number of steppers and their values are also connected with some model, you should use FileManager to save encoded values of steppers or you can also use some database like CoreData or Realm.
I'm a software development student and for a school project me and a friend are making a iOS Swift game and we are learning Swift 3 as we progress in the game aspects.
Now, we have come to the part of the development where we question how is game data going to be saved (I'm talking about scores, player's name, in-game money, if the player plays in mute or unmute.. you know that kind of stuff)
The game uses an avatar and the player can customize it, so data customization needs to be saved too.
Right now we manage this data throught variables like
var eyeColor = "#04ff45"
var eyetype = 3 // And so on
I have done some research on this and found that there are various methods we could use.
Like, we could use Core Data or a Dictionary or a JSON file.
I'd like to know which could be the best/easiest way to acomplish this, if we need to use any specific libraries and some basic code on how to write/read the data
Thank you very much
Best way to save scores is by using NSUserDefaults
To save settings such as volume, you can follow the model I have below.
//When you tap on the mute button, execute this code.
if soundSwitch { //true
UserDefaults.standard.set(false, forKey: "SoundSwitch")
soundSwitch = false
} else { //false
UserDefaults.standard.set(true, forKey: "SoundSwitch")
soundSwitch = true
}
If you are saving players money, name and all this other stuff, it would be better to save them in some kind of database. I'm not sure if you can do that with GameCenter.
The easiest way to save data you are working with on the device would be to use NSUserDefaults. All you have to do is create a key, and store a value under that key. You can then use the key to access the value later and it is stored on the phone's permanent memory.
For example, you would use the user defaults to create a key called "eye color", store a value under that key, and then access it later using the term that you know the value is stored under (i.e. the key). This is a very simple way of storing such information.
This question already has answers here:
How to save local data in a Swift app?
(12 answers)
Closed 6 years ago.
In total I have 2 viewcontrolers. The App is the same like this guy made in a tutorial. https://www.youtube.com/watch?v=LrCqXmHenJY&t=40s
To make a start, I made a var:
import UIKit
var list = ["Task 1", "Task 2", "Task 3", "Task 4"]
class FirstViewController: UIViewController , UITableViewDelegate, UITableViewDataSource{
My current problem is, that when I close the app no ToDo's which I created were saved.
What do I need to do to save my var list so that my ToDo-List isn't empty when I open it for the next time?
You can use UserDefaults to save/load application state or configurations. For complex requirements use CoreData
Writing/Saving before app termination
let defaults = UserDefaults.standard
defaults.set(true, forKey: "Enabled")
Reading/Loading on app launch
let defaults = UserDefaults.standard
let enabled = defaults.bool(forKey: "Enabled")
Read the related Apple docs here.
If you want an easy way to store a list of strings, you can use UserDefaults. Another way to do this is to use Core Data which is more difficult to use. It is usually used to store more complex data structures than an array of strings.
To save the string array to UserDefaults, do this:
UserDefaults.standard.set(list, "myStringArray")
You can replace "myStringArray" with any key you want.
To retrieve it, do this:
list = UserDefaults.standard.stringArray(forKey: "myStringArray")
I suggest you save the array in this method in App Delegate:
func applicationDidEnterBackground(_ application: UIApplication) {
}
For more info on User Defaults, see https://developer.apple.com/reference/foundation/userdefaults
You have very simple needs. Look at NSUserDefaults (now called UserDefaults in Swift 3.)
Save your data to UserDefaults when it changes, and read it back when you display your view controller.
As Eric says in his comments, make list an instance variable of your view controller.
EDIT:
In the comments below, rmaddy pointed out that the app will be saving a to-do list. That will likely grow in complexity from an array of a handful of items to a larger array or potentially a more complex structure.
Given that, you might want to look at saving your data to a plist file in the documents directory (quite simple) or using NSCoding if you have custom objects other than the small list of "property list" types that can be saved to a plist.
Both of those solutions read and write the data all at once to a file. That might be ok for a to-do list app.
If you need to change parts of a larger data-set and leave the rest unchanged then it's time to consider a database like Core Data.
I'm working on my first app and I need some help understanding what kind of data storage I need. I'm familiar with PHP, SQL, and databases but I don't know where to start with this project.
The app is pretty much a basic form with text fields, pickers, and uploaded images. At the end, the user will press submit and all of their data will be sent in an email.
What is the best way to store their data, so the user can go to previous screens and have their previously entered info still there. And then what is the best way to store the data after they press submit to send it in an email?,
Thanks so much for your help!
If it's just form data that you're storing once for submission, for simplicity sake, I recommend just stuffing it in a global dictionary that you can access from different views. Swift makes this easy by just adding an empty swift file and defining your dictionary at the top:
var myFormData: [String: AnyObject]()
You can now access "myFormData" form anywhere in your app, add and remove stuff from it.
You shouldn't technically need to "reload previous views" because of the way the navigation stack works. Anything you go back to should hold it's info.
If you really need to save the data to allow the user to close the app and then pick up where they left off much later, then I recommend simply kicking your dictionary to NSUserDefaults. It doesn't sound like something that needs to involve a database.
You can use a class called NSUserDefaults
var defaults: NSUserDefaults = NSUserDefaults.standardUserDefaults() //make an instance
defaults.setObject("Bob", forKey: "myName") //storing a value
defaults.synchronize() //synchronize data
println(defaults.objectForKey("myName")!) //retrieve the data