Swift nil coalescing operator with array - arrays

Question

I am trying out an exercise in creating a simple todo list.
Before introducing Realm or coreData i wanted to test it out and see if everyting is going smoothly.
I know i probably can make this work with some if conditions but i would love to be able to use the nil coalescing operator (i just love the simplicity of it), and i am not sure why its not working.
I made it work without it, but really interested what is the reason it is behaving like this.
When i launch the app it just shows "No Category Added" even after i add some items to the array and print them out, list stays the same.
import UIKit
class CategoriesTableView: UITableViewController {
var testData = [FauxData]()
override func viewDidLoad() {
super.viewDidLoad()
tableView.reloadData()
}
// MARK: - Data Methods
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
let data = testData[indexPath.row].categoryTitle ?? "No Category Added"
cell.textLabel?.text = data
return cell
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return testData.count
}
#IBAction func addItem(_ sender: UIBarButtonItem) {
CreateNewItem(item: "test")
tableView.reloadData()
}
func CreateNewItem(item: String) {
let newItem = FauxData()
newItem.categoryTitle = item
testData.append(newItem)
print(item)
}
}
This is the class FauxData:
class FauxData {
var categoryTitle: String?
}
Sry if this is too simple or a duplicate, i wasn't able to find and appropriate answer.

Answer 1

Unfortunately, indexing an empty array crashes instead of returning nil, so you can't use the nil coalescing operator. Instead, use the .isEmpty property along with the ?: operator to achieve your goal:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
let data = testData.isEmpty ? "No Category Added" : testData[indexPath.row].categoryTitle
cell.textLabel?.text = data
return cell
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return testData.isEmpty ? 1 : testData.count
}
Note: You have to return 1 from tableView(_:numberOfRowsInSection:) when the array is empty so that tableView(_:cellForRowAt:) will be called to return your default message.
If you implement safe array indexing, you could then use the nil coalescing operator:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
let data = testData[safe: indexPath.row]?.categoryTitle ?? "No Category Added"
cell.textLabel?.text = data
return cell
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return testData.isEmpty ? 1 : testData.count
}