Swift 4 delegates and passing textfield data - swift

Question

I am trying to make an app using the GoogleBooks API where I can use either a title or author or both to search for books. I am currently just working on the delegate portion to be able to pass the search terms to the results table view. However, I am getting errors with the variables I am using being let constants but I have them declared as var so I'm not sure where I am messing up.
This is the UIViewController code for the view with the two search boxes and the button:
import UIKit
protocol ViewControllerDelegate: class {
func searchInput(_ titleFromSearch: String?, authorFromSearch: String?)
}
class ViewController: UIViewController {
#IBOutlet weak var titleFromSearch: UITextField!
#IBOutlet weak var authorFromSearch: UITextField!
weak var delegate: ViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
titleFromSearch.delegate = self
authorFromSearch.delegate = self
}
override func touchesEnded(_ touches: Set<UITouch>, with event:
UIEvent?) {
super.touchesEnded(touches, with: event)
titleFromSearch.resignFirstResponder()
authorFromSearch.resignFirstResponder()
}
}
extension ViewController: UITextFieldDelegate {
func fieldsDidEndEditing(_ titleEntered: UITextField, authorEntered:
UITextField) {
if let delegateController = delegate {
delegateController.searchInput(titleFromSearch.text,
authorFromSearch: authorFromSearch.text)
}
}
}
And this is the code for the TableViewController that I have set up for the results to be displayed in.
import UIKit
import GoogleBooksApiClient
class SearchResultsTableViewController: UITableViewController {
var titleFromSearch: String?
var authorFromSearch: String?
var data = [Volume]()
override func viewDidLoad() {
super.viewDidLoad()
let session = URLSession.shared
let client = GoogleBooksApiClient(session: session)
let req = GoogleBooksApi.VolumeRequest.List(query: "Google")
let task: URLSessionDataTask = client.invoke(
req,
onSuccess: { [weak self] volumes in
self?.data = volumes.items
self?.tableView.reloadData()
},
onError: { error in
print("\(error)") }
)
task.resume()
}
// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection
section: Int) -> Int {
return data.count
}
override func tableView(_ tableView: UITableView, cellForRowAt
indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell",
for: indexPath)
let item = data[indexPath.row]
cell.textLabel?.text = item.volumeInfo.title
cell.detailTextLabel?.text = item.volumeInfo.authors.first
return cell
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
super.prepare(for: segue, sender: sender)
if let destination = segue.destination as? ViewController {
destination.delegate = self
}
}
}
Here is where I get the let constant error is with these two assignment statements:
extension SearchResultsTableViewController: ViewControllerDelegate {
func searchInput(_ titleFromSearch: String?, authorFromSearch: String?)
{
titleFromSearch = titleFromSearch
authorFromSearch = authorFromSearch
}
}
I added all the code because as I said I am new to iOS and I'm not sure where this error stems from in the code.

Answer 1

In the two lines causing your errors:
titleFromSearch = titleFromSearch
authorFromSearch = authorFromSearch
you are attempting to assign the parameters to themselves. You want to set the parameter values to your properties of the same name. To do this, add self. to the property references:
self.titleFromSearch = titleFromSearch
self.authorFromSearch = authorFromSearch