Adding element to UITableView - ios

Question

I am trying to add an element into the array cart.
After executing this function more than once on different items, I see from the print statement that the count never increases and always stay at 1. Furthermore, the new element replaces the old element rather than appending to the array.
Additionally, I don't know how to display the data into the table view of cartTableViewController. Whenever I navigate to cartTableViewController, no elements show up.
#IBAction func addToCart(_ sender: UIBarButtonItem) {
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
if let cartTableViewController = mainStoryBoard.instantiateViewController(withIdentifier: "CartTableView") as? CartTableViewController {
var cart = cartTableViewController.cartItems
let itemToAdd = CartItem(product: product!, quantity: quantity)
print(itemToAdd!.product.itemName) // the new item replaces the existing one
cart.append(itemToAdd!)
print(cart.count) // count is always 1
print(quantityLabel.text! + " " + (product?.itemName)! + " added")
}
}

Answer 1

Try this may help you,
var cart: [CartItem]!
override func viewDidLoad() {
super.viewDidLoad()
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
if let cartTableViewController = mainStoryBoard.instantiateViewController(withIdentifier: "CartTableView") as? CartTableViewController {
cart = cartTableViewController.cartItems
}
}
#IBAction func addToCart(_ sender: UIBarButtonItem) {
if cart != nil {
let itemToAdd = CartItem(product: product!, quantity: quantity)
print(itemToAdd!.product.itemName) // the new item replaces the existing one
cart.append(itemToAdd!)
print(cart.count) // count is always 1
print(quantityLabel.text! + " " + (product?.itemName)! + " added")
}
}

Answer 2

I can clearly say that you have a problem with the below line because the value of cartTableViewController.cartItems always nil or empty
let cartTableViewController = mainStoryBoard.instantiateViewController(withIdentifier: "CartTableView") as? CartTableViewController
var cart = cartTableViewController.cartItems
Every time, You have to use old instead of the initialized new object.
You can fix your problem defining a global array of the cart which is
accessible throughout app.
Code:
let cartTableViewController = mainStoryBoard.instantiateViewController(withIdentifier: "CartTableView") as? CartTableViewController
var cart = aryCart //Your cart global object
print(cart.count) // Updated Count
Update:
Just define a variable outside of class then it will automatically accessible throughout application.
var aryCart = [CartItem]()
class CartVC:UIViewController{
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func addToCart(_ sender: UIBarButtonItem) {
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
if let cartTableViewController = mainStoryBoard.instantiateViewController(withIdentifier: "CartTableView") as? CartTableViewController {
let itemToAdd = CartItem(product: product!, quantity: quantity)
print(itemToAdd!.product.itemName) // the new item replaces the existing one
aryCart.append(itemToAdd!)
print(aryCart.count) // count is always 1
print(quantityLabel.text! + " " + (product?.itemName)! + " added")
}
}
}

Answer 3

The new array you're creating only exists within the scope of the function. When assigning cart to cartTableViewController.cartItems, this only copies the values from cartItems into cart, it doesn't assign the pointer. For example:
var cartItems = ["First element"]
var cart = cartItems
cart.append("Second Element")
print(cartItems)
print(cart)
This would print:
["First element"]
["First element", "Second Element"]
It looks like you're adding data to an array in another ViewController. I would generally advise you to update state through some other mechanism than the instance variable in the other view controller. There are many philosophies about how to structure code in the best way, one solution for you could be to use the MVVM pattern. This article covers it: https://medium.com/#azamsharp/mvvm-in-ios-from-net-perspective-580eb7f4f129
A quick way to "clean up" a little bit would be to have an intermediate object where you store the cartItems data, which you have a reference to in both the current view controller and CartTableView, such as CartItemStore:
class CartItemStore {
static let shared = CartItemStore()
private let cartItems: [CartItem]
// you can add logic for reading previously added cart items from cache in order to persist it.
// The same goes when adding new cartItems
private init() {
self.cartItems = []
}
func getItem(_ index: Int) -> CartItem? {
//Check whether the index passed in is valid
if cartItems.indices.contains(index) {
return cartItems[index]
} else {
return nil
}
}
func addItem(_ item: CartItem) {
cartItems.append(item)
}
func numberOfItems() -> Int {
return cartItems.count
}
}
Then you can use your singleton store in the following way:
// This inside the current view controller
private let cartItemStore = CartItemStore.shared
#IBAction func addToCart(_ sender: UIBarButtonItem) {
...
let itemToAdd = CartItem(product: product!, quantity: quantity)
cartItemStore.addItem(itemToAdd)
print(cartItemStore.numberOfItems())
}
Then you can read items from the other view controller as well by accessing the singleton.
Singletons should generally be avoided since it can be hard to test your application. Singletons allow state to be updated wherever, which can create a nightmare if you abuse it good enough. I used it here to give you a quick way to accomplish something that is a little less coupled, but if you will sit with this code base for a while you might want to rethink this. Feel free to look into MVVM and how to manage state with it, it will make things easier, in the long run, to have a structured way of managing state in your application :) Hope this is to any help of you.