Button only works when tapped twice - swift

Question

I have two buttons that each have a different segue to a different view controller, which is only triggered if certain conditions are met. For some reason, one of the buttons works fine, the other button has to be tapped twice in order for it to segue to the next view controller. The strange part is that the code for both buttons and segue if conditions are copied and pasted and slightly modified to go to their respective vcs. How can I get both buttons to work on the first tap?
So far I've tried:
reordering the button functions
reordering the segue functions
deleting/reconnecting the button
deleting/reconnecting the button
I believe it has something to do with the following code because when I remove it, this behavior is gone and a different but similar feature in the app with virtually the same code (minus the part below) works just fine. I do need it however due to testing for nil/errors:
override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
return nextButton
}
Here is the code
import UIKit
class bathShowerMeasurementViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.hideKeyboardWhenTappedAround()
}
var nextButton = false
#IBOutlet weak var inchesButton: UIButton!
#IBAction func inches(_ sender: UIButton) {
if sender.isSelected {
sender.isSelected = false
} else {
sender.isSelected = true
}
}
#IBOutlet weak var unitError: UILabel!
#IBOutlet weak var centimeterButton: UIButton!
#IBAction func centimeter(_ sender: UIButton) {
if sender.isSelected {
sender.isSelected = false
} else {
sender.isSelected = true
}
}
#IBOutlet weak var length: UITextField!
#IBOutlet weak var lenghtError: UILabel!
#IBOutlet weak var width: UITextField!
#IBOutlet weak var widthError: UILabel!
#IBOutlet weak var height: UITextField!
#IBOutlet weak var heightError: UILabel!
#IBAction func showerCalc(_ sender: UIButton) {
let widthTub = Double(width.text!)
let lengthTub = Double(length.text!)
let heightTub = Double(height.text!)
var enableNextButton = true
if widthTub == nil || widthTub == 0.0 {
widthError.text = "Enter Width"
enableNextButton = false
}
if heightTub == nil || heightTub == 0.0 {
heightError.text = "Enter Height"
enableNextButton = false
}
if lengthTub == nil || lengthTub == 0.0 {
lenghtError.text = "Enter Length"
enableNextButton = false
}
switch (inchesButton.isSelected, centimeterButton.isSelected) {
case (false, false):
unitError.text = "Please Select A Unit"
enableNextButton = false
case (true, true):
unitError.text = "Only Select One Unit"
enableNextButton = false
default: break
}
nextButton = enableNextButton
}
#IBAction func goToShower(_ sender: UIButton) {
let widthTub = Double(width.text!)
let lengthTub = Double(length.text!)
let heightTub = Double(height.text!)
var enableNextButton = true
if widthTub == nil || widthTub == 0.0 {
widthError.text = "Enter Width"
enableNextButton = false
}
if heightTub == nil || heightTub == 0.0 {
heightError.text = "Enter Height"
enableNextButton = false
}
if lengthTub == nil || lengthTub == 0.0 {
lenghtError.text = "Enter Length"
enableNextButton = false
}
switch (inchesButton.isSelected, centimeterButton.isSelected) {
case (false, false):
unitError.text = "Please Select A Unit"
enableNextButton = false
case (true, true):
unitError.text = "Only Select One Unit"
enableNextButton = false
default: break
}
nextButton = enableNextButton
}
override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
return nextButton
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let bathLength = Double(length.text!)
let bathWidth = Double(width.text!)
let bathHeight = Double(height.text!)
let water = Double(bathLength! * bathWidth! * bathHeight!)
if (segue.identifier == "showerCalc") {
if inchesButton.isSelected == true{
let bathWater = water / 231
let destinationVC = segue.destination as! showerFillMethodViewController
destinationVC.bathFlow = String(bathWater)
}
if centimeterButton.isSelected == true{
let bathWater = water / 3785.41
let destinationVC = segue.destination as! showerFillMethodViewController
destinationVC.bathFlow = String(bathWater)
}
}
if (segue.identifier == "showerTool") {
if inchesButton.isSelected == true{
let bathWater = water / 231
let destinationVC = segue.destination as! showerFlowMainViewController
destinationVC.bathFlow = String(bathWater)
}
if centimeterButton.isSelected == true{
let bathWater = water / 3785.41
let destinationVC = segue.destination as! showerFlowMainViewController
destinationVC.bathFlow = String(bathWater)
}
}
}
}