How to use delegates to communicate data from a custom cell to a label in the parent view - ios

Question

I have figured out how to pass data between views with delegates in other situations but this one is stumping me.
In this example I am trying to send data resulting from pressing a button, up to the label using a delegate pattern but without any success. My guess is that I am missing something fundamental here and I haven't found any examples that deal with delegates in quite this way.
//
// ViewController.swift
// TableCellDelegate
//
// Created by Chris Cantley on 6/1/15.
// Copyright (c) 2015 Chris Cantley. All rights reserved.
//
import UIKit
class ViewController: UIViewController, CellInfoDelegate {
var cellViewController = CellViewController()
//The place to put the number into.
#IBOutlet weak var sumLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
cellViewController.delegate = self
}
//2)...to here.
func processThatNumber(theNumber: Int) {
println("out : \(theNumber)")
}
}
// Table View delegates
extension ViewController: UITableViewDataSource, UITableViewDelegate
{
//One row
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 1
}
// Load custom cell
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("thisCustomCell", forIndexPath: indexPath) as! CellViewController
return cell
}
}
//-------------------- Protocol for Delegate -----------------------
protocol CellInfoDelegate {
func processThatNumber(theNumber: Int)
}
//-------------------- Cell to Pass info to Parent -----------------------
class CellViewController: UITableViewCell{
var sumNumber: Int = 0
var delegate: CellInfoDelegate?
#IBAction func addButton(sender: AnyObject) {
// increment that number
self.sumNumber += 5
//1) I want to get it from here...... but delegate ends up nil
if let delegate = self.delegate {
delegate.processThatNumber(self.sumNumber)
}
//Shows that the number is incrementing
println(sumNumber)
}
}
The ViewController and CellViewController are connected to their respective classes
Thanks in advance.

Answer 1

You should set the delegate here:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("thisCustomCell", forIndexPath: indexPath) as! CellViewController
cell.delegate = self // <-- Set the delegate.
return cell
}

Answer 2

Thanks to i_am_jorf for the solution, here is the code that works.
//
// ViewController.swift
// TableCellDelegate
//
// Created by Chris Cantley on 6/1/15.
// Copyright (c) 2015 Chris Cantley. All rights reserved.
//
import UIKit
import Foundation
class ViewController: UIViewController, CellInfoDelegate {
//The place to put the number into.
#IBOutlet weak var sumLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
//2)...to here.
func processThatNumber(theNumber: Int) {
println("out : \(theNumber)")
self.sumLabel.text = toString(theNumber) as String
}
}
// Table View delegates
extension ViewController: UITableViewDataSource, UITableViewDelegate
{
//One row
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 1
}
// Load custom cell
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("thisCustomCell", forIndexPath: indexPath) as! CellViewController
//SOLUTION : put the Delgate HERE in the place where the cell is instantiated so that there is a connection back
// to this class from the Cell class
cell.delegate = self
return cell
}
}
//-------------------- Protocol for Delegate -----------------------
protocol CellInfoDelegate {
func processThatNumber(theNumber: Int)
}
//-------------------- Cell to Pass info to Parent -----------------------
class CellViewController: UITableViewCell{
var sumNumber: Int = 0
var delegate: CellInfoDelegate?
#IBAction func addButton(sender: AnyObject) {
// increment that number
self.sumNumber += 5
//1) I want to get it from here...... but delegate ends up nil
if let delegate = self.delegate {
delegate.processThatNumber(self.sumNumber)
}
//Shows that the number is incrementing
println(sumNumber)
}
}

Answer 3

Do you need to use Delegates?
What if you have this function output a number:
func processThatNumber(theNumber: Int) -> Int {
println("out : \(theNumber)")
return theNumber
}
Then set the text on the label using the button:
#IBAction func addButton(sender: AnyObject) {
self.sumNumber += 5
sumLabel.text = "\(processThatNumber(self.sumNumber))"
println(sumNumber)
}
Would that work for you?