I have data sent back to my VC using the delegate method. How can I possibly store it so then I can use it to send to another VC?
func DataToPass(ArrayName: [String]) { //function from delegate
Datacollect = ArrayName
print(ArrayName)
}
Here's the function used in the delegate method that holds my data. ArrayName is an array containing my data.
Datacollect is an attempt to collect it, however nothing gets stored in Datacollect.
I have already assigned Datacollect as a String array.
var Datacollect = [String]()
How can I store the data to my VC from ArrayName?
There are lot of ways of storing data and one of the simplest ways to get started is to use the built-in UserDefaults.
This is how you might use the following code inside a method to store your DataCollect array.
Let defaults = UserDefaults.standard
defaults.set(DataCollect, forKey: "DataCollect")
To retrieve the data you could use the following code inside a method:
let defaults = UserDefaults.standard
let DataCollect = defaults.array(forkey: "DataCollect")
Related
To save some data to UserDefaults first we must encode it as JSON using JSONEncoder, which will send back a Data instance we can send straight to UserDefaults.Then reading saved data is a matter of converting from Data using a JSONDecoder. But sometimes we dont have to do that.
My question is will that method work anytime and when do i have to use it because i found this other solution without encode and decode:
var allWords = [String]()
var usedWords = [String]()
var currentWord: String?
In viewDidLoad:
let defaults = UserDefaults.standard
if let presentWord = defaults.object(forKey: "presentWord") as? String,
let savedWords = defaults.object(forKey: "savedWords") as? [String] {
title = presentWord
currentWord = presentWord
usedWords = savedWords
print("Loaded old game!")
Save method:
func save() {
let defaults = UserDefaults.standard
defaults.set(currentWord, forKey: "presentWord")
defaults.set(usedWords, forKey: "savedWords")
}
It's simple and faster way but Im not sure when i can use it with no worries
UserDefaults storage is a property list. NSString, NSData, NSArray, and NSDictionary are the only Cocoa classes that can be expressed directly in a property list. Moreover, an NSArray or NSDictionary can be expressed in a property list only if its elements are instances of those classes, along with NSDate and NSNumber. Those are the property list types.
If your Swift type bridges to a property list type, you can store it directly. So String will bridge to NSString, and an array of String will bridge to an NSArray of NSString, so you can store them directly.
But if what you've got is not a property list type, you need to transform it into a property list type before you can store it, and the usual solution is to transform it into an NSData (Swift Data). You don't have to use JSONEncoder for that but you do need to do it somehow.
I am new to macOS Development and I am working on a project for macOS using Xcode 10 and Swift 4.2.
The project contains mainly 3 view controllers.
Firstly, ViewController (the main welcome screen which separates the other two) has two buttons to call the other two respectively.
Secondly, MakeEntry View Controller creates an array of strings data variable using a form type structure comprised of text views and save button etc. which in the end just saves all input data into an array of strings data variable called carrierArray
Thirdly, there is a split view controller for displaying two children view controller namely EntryList and EntryDetail
EntryList (the left pane) contains a Table View to display titles of entries and EntryDetail (the right pane) will contain the description of the title entry (somewhat like the default notes app of macOS)
I want to achieve a simple functionality of being able to access or read that Array of strings variable called carrierArray which is created when the MakeEntry view controller saves it into a global variable defined within its own class file But I want to access that array of strings anywhere and anytime later.
I cannot use delegates and protocols, closures, segues or storyboard identifiers to carry that data because I am not navigating to the Split View Controller straightaway and also because I want to store that data
to manipulate it further before displaying it in the right pane of split view controller (EntryDetail) .
I am unable to figure out whether how it might be possible to achieve this functionality using NSUserDefaults or CoreData.
Therefore I tried using the Notification Centre after storing that array of Strings in a Dictionary namely notifDictionary containing a key called carryData to be stored as the data object of notification centre And with some research and some trials and errors but without any luck all resulting in failure to get that data in the split view controller left pane class file namely (EntryDetail).
Code Snippets are as below, thanks a lot in advance for the kind help.
In MakeEntry View controller:
notifDictionary = ["carryData": carrierArray]
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "dataCarrier") , object: nil, userInfo: notifDictionary)
In EntryList View Controller:
(Tried using both types of selector methods one at a time and even using them together but all without luck! Please Help!)
The Variable datumDict and datumArray and nothing but copy receivers for carrierArray and notifDictionary
var datumDict: [String:[String]] = [:]
var datumArray: [String] = []
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(self.getThatDict(_:)), name: NSNotification.Name(rawValue: "dataCarrier") , object: nil)
NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "dataCarrier") , object: nil, queue: nil, using: catchNotification)
//datumArray = datumDict["carryData"]!
}
#objc func onNotification(notification:Notification)
{
print(notification.userInfo!)
}
func catchNotification(notification: Notification) -> Void
{
let theDict = notification.object as! NSDictionary
datumDict = theDict as! [String: [String]]
guard let theData = notification.userInfo!["carryData"] as? [String:[String]] else { return }
datumDict = theData
}
#objc func getThatDict(_ notification: NSNotification)
{
print(notification.userInfo ?? "")
if let dict = notification.userInfo as NSDictionary?
{
if let thatDict = dict["carryData"] as? [String: [String]]
{
datumDict = thatDict
}
}
}
With the caveat that "globals and singletons should be avoided," it sounds like they are a good fit for what you're trying to do. As you get more comfortable in Cocoa you can move into more sophisticated means of accomplishing this (dependency injection). Look into this as you get more comfortable with Cocoa.
Create a simple singleton type:
// AppState.swift
class AppState {
// Basic singleton setup:
static let shared = AppState()
private init() {} // private prevents instantiating it elsewhere
// Shared state:
var carrierArray: [String] = []
}
Access it from your view controllers:
// YourViewController.swift:
#IBAction func doSomething(_ sender: Any) {
AppState.shared.carrierArray = ...
}
If you need to update the other view controllers when this shared state changes, notifications are a good tool for that. You could do this with a didSet on carrierArray, or simply trigger the notification manually.
I have saved an array of custom objects that conforms to NSCoding protocol in UserDefaults using NSKeyedArchiver. But when I try to retrieve it using NSKeyedUnarchiver, i get runtime errors from Xcode. I have tried initialising NSArray using unarchived data but it also failed. My guess is that while unarchiving swift doesn't understand custom elements of this array. How shall I do it?
This is how I archived array of custom objects
static func saveCategoryList(_ categoryList : [Category]!) -> Void{
let userDefaults = UserDefaults.standard
let categoryListData = NSKeyedArchiver.archivedData(withRootObject: categoryList)
userDefaults.set(categoryListData, forKey: Constants.CategoryList)
userDefaults.synchronize()
}
I get error like the attached screenshot in runtime. I am quite sure I am not doing it right. How can get my desired result?
Okay, so basically I am following a tutorial on udemy on how to create a chat with Backendless and Firebase. However, I prefer not to use Backendless, because I don't want to rely on 2 providers - so I want to stick to Firebase only. Therefore, I am currently converting my code to Firebase.
I have a view controller that displays a unique page for each UID - from a database that I have. The UID is stored as a String, and is assigned upon a segue from another table view controller (this works fine). After that, I fetch the data that I want from the user, with the UID. I have a "Start Chat" button that is supposed to create a new chat.
In this tutorial, the tutor has set a protocol (delegate) that is triggering another function from another view controller. This is what it looks like:
protocol ChooseUserDelegate {
func createChatroom(withUser: String)
}
var delegate: ChooseUserDelegate!
and in my chat #IBAction, I have this code:
#IBAction func StartChat(sender: AnyObject) {
let userID = uid
if let theId = userID as? String {
delegate.createChat(String(theId))
}
}
(The code above is all in the same VC.).
In another view controller, where the createChat() function is stored, is the following code:
class AnotherVC UIViewController, UITableViewDelegate, UITableViewDataSource, ChooseUserDelegate{
func createChat(withUser: String) {
print(withUser)
}
}
The problem is that I can't get to call createChat(), because of an optional error (unwrapping) on the delegate.createChat(String(theId)).
Edit: Even with a "" input, I get an error. I am really confused now. Is it something wrong with my delegate?
The only part of your code that is optional is delegate (because you correctly unwrapped userID). Therefore, the error must be due to delegate being nil. Make sure that you set delegate before calling StartChat().
The line var delegate: ChooseUserDelegate! does not initialize a delegate. When you write ChooseUserDelegate! you are only defining the type of the delegate variable. It is automatically set to nil. To initialize a new instance of ChooseUserDelegate you would need to write something like:
var delegate: ChooseUserDelegate! = ChooseUserDelegate()
There are a few other ways you could clean up your code. Method names should be llamaCase, not CamelCase, so you should rename StartChat() to startChat() (be sure to reconnect in interface builder). The body of that method has three different names for the same variable, uid. See how simple it could be:
#IBAction func startChat(sender: AnyObject) {
if let uid = uid as? String {
delegate.createChat(uid)
}
}
if let theId = userID {
delegate.createChat(String(theId))
}
Im having a hard time understanding data passing with delegates, I have looked but I get confused by the answers as I'm usually trying to do the opposite of what needs to be done for mine.
What I am trying to do is pass a PFObject from my main viewController (a UITableView) to a PopOverViewController.
I have done this successfully, but I need to pass the object. What would be the best way to pass from the mainController (SOITableViewController) to the popover (DetailPopViewController)?
Where should the protocol go? Where should the Delegate method be placed, etc.
Thank you!
PrepareForSegue, NSUserDefault and Singleton
You have a few possible options to pass your data to other views depending how you want that data to be handled, I will explain each for you and you can choose which one best fit your need.
prepareForSegue: Method
I recommend this method if you want to hold your data for 1 segue transition, it's a good cause to pass this again to another view afterward you need to create another prepareForSegue within the new view. here is an example on how to do this:
First, you create 2 variables in both views, 1 to send (currentViewController.swift) and 1 to receive (toViewyourGoingController.swift).
currentViewController.swift var dataToSend: AnyObject?
ViewYourGoingController.swift var dataToReceive: AnyObject?
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
//Check your segue, this way you can transfer different data to different view. also make sure the identifier match your segue.
if segue.identifier == "toViewYourGoing" {
//Initial your second view data control
let ExchangeViewData = segue.destinationViewController as! toViewyourGoingController
//Send your data with segue
ExchangeViewData.dataToReceive = dataToSend
}
}
NSUserDefault
Now this method is good if you want to keep your data live as long as the app is installed, once the app is removed this will reset automatically. You also have the option to update the value of the key if you wish, here is how you do NSUserDefault:
I always like to register my NSUserDeafult to default setting, a lot of people just continue with the second step without registering.
Register NSUserDefault in AppDelgate.swift
NSUserDefaults.standardUserDefaults().registerDefaults(["valueName": AnyObject])
Set Value to your NSUserDefault, this depends on what type of data you're storing, should match the one with your registration if you did register. (Example of Boolean data type below)
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "valueName") //Bool Data Type
Make sure you synchronize once you set the value to the NSUserDefault, this way it will update instantly, otherwise it will update when it get a chance.
NSUserDefaults.standardUserDefaults().synchronize()
Receive Value: this will receive boolean value since we set boolean and register boolean.
let Variable: Bool! = NSUserDefaults.standardUserDefaults().boolForKey("valueName")
Singleton
Now singleton is basically a global variable that you can use them in any views, but some developers experience some bugs and difficulties, use it at your own risk, I recommend this method when you're definite that you will use that data a lot (STILL RISKY), but this method is like goddess of data handling :).
Create a NSObject subclass and call it DataManager.swift (I call it data manager cause it handle data.) as following:
import UIKit
class DataManager: NSObject {
//Store Data Globally
static var someData: Boo! //This Boolean, you can choose whatever you want.
}
the static is what keep your data live.
Now you can store and receive someData from anywhere like you handle any data type like this.
//Store
DataManager.someData = true
//Receive
print(DataManager.someData)
Challenges:
You can also use
Keychain
Sergey Kargopolov will walk you through how to use a third party to use swift keychain. Otherwise, you can take even harder challenge and create one yourself :P .
Key-Value Data in iCloud
The best way to do this would be to pass it over when you do the prepare for segue method. So to do this make a variable in your detailPopViewController. In this case your pop over segue in storyboard will have the segue identifier detailView. Also tblSearchResults is your tableView outlet (you can name it whatever you want). Is that what you were looking for?
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "detailView" {
if let detailViewController = segue.destinationViewController as? PopOverViewController{
if let indexPath = self.tblSearchResults.indexPathForCell(sender as! SOITTableViewController) {
detailViewController.objectInSecondVC = objectFromFirstVC[indexPath.row]
}
}
}
}