IOS Swift: Using delegate methods in custom class - ios

Question

I am trying to create a bar graph class in swift but having difficulty setting up a delegate....heres what I have so far...
BarChart.swift:
import Foundation
import UIKit
#objc protocol BarChartDelegate {
optional func barChart(colorForBarAtIndex index: Int) -> UIColor
}
class BarChart : BarChartDelegate {
let data : [NSDecimalNumber]
let container = UIView()
var barWidth : CGFloat = 100
var barSpacing : CGFloat = 10
var delegate : BarChartDelegate?
init(data: [NSDecimalNumber], frame: CGRect) {
self.data = data
self.container.frame = frame
drawGraph()
}
func drawGraph() {
var i = 0
for item in self.data {
var bar = UIView()
let xPos = CGFloat(i)*self.barWidth
bar.frame = CGRectMake(xPos, 0, self.barWidth, 100)
if let del = delegate? {
bar.frame
println(del.barChart!(colorForBarAtIndex: i))
bar.backgroundColor = del.barChart!(colorForBarAtIndex: i)
}
else {
println("nope!")
}
self.container.addSubview(bar)
i++
}
}
}
ViewController.swift
class ViewController: UIViewController, BarChartDelegate {
var colors = [
UIColor.greenColor(),
UIColor.blueColor(),
UIColor.redColor()
]
override func viewDidLoad() {
super.viewDidLoad()
var barChart = BarChart(data: [NSDecimalNumber(double: 100.00), NSDecimalNumber(double: 200.00), NSDecimalNumber(double: 300.00)], frame: CGRectMake(0, 0, 400.00, 100.00))
self.view.addSubview(barChart.container)
}
func barChart(colorForBarAtIndex index: Int) -> UIColor { // this is not running?
return self.colors[index]
}
}
the delegate method in my ViewController.swift file is not being run and I just get "nope!" printed to the console 3 times... which is a result of the delegate optional finding nil when unwrapping?
Is there something I am missing here?
Any help would be appreciated!
Thanks,
Dave

Answer 1

First off, it rarely makes sense for a BarChart to also be a BarChartDelegate. You don't delegate things to yourself!
Second, as far as I can tell you're not actually setting the ViewController as the delegate of the BarChart. Simply adopting the BarChartDelegate protocol is not enough to do that; you need to set it explicitly.
So, for example, you might want to do this after you create the BarChart:
var barChart = ...
barChart.delegate = self
Alternatively, if the delegate is vital for your chart, you might want to change the constructor to accept a delegate as an argument.