Use of Unresolved Identifier with Segmented Control

I have a scene in my app that I want to do basic math between two slider bars and a segmented control that the user picks. I am trying to do the math between variables under the segmented controls, but Xcode is giving me a (!) stating

Use of unresolved identifier "xxxx"

with whatever variable I'm trying to add. My code is:

import UIKit

class DopamineCalculator: UIViewController {

//slider outlets
@IBOutlet weak var slider: UISlider!
@IBOutlet weak var sliderone: UISlider!
//segmentoutlet
@IBOutlet weak var segmentoutlet: UISegmentedControl!


//LABELS
//weight label
@IBOutlet weak var weightlabel: UILabel!
//dosage label
@IBOutlet weak var dosagemg: UILabel!
 //Drip Rate Answer Label
@IBOutlet weak var dripanswer: UILabel!




//ACTIONS!!
//weight slider action
@IBAction func weightslider(sender: UISlider) {

    let weight = Int(sender.value)
    //converts to kgs
    let kgs = Int(sender.value) / Int(2.2)

    weightlabel.text = "(weight) lbs"
}


//Dosage Desired dosage slider

@IBAction func dosagedesired(sender: UISlider) {

    let dosage = Int(sender.value)



    dosagemg.text = "(dosage) mg"
}


//CONCENTRATION OPTIONS
@IBAction func concentrationoption(sender: UISegmentedControl) {
        switch segmentoutlet.selectedSegmentIndex
        {
        case 0:


            dripanswer.text = (kgs) * (dosage) / 800


        case 1:


            dripanswer.text = "1600";



        case 2:


            dripanswer.text = "3200";

        default:
            break;
    }
}

What I am trying to do is kgs x dosage / 800 respectively for each case. I can not find an adequate solution online to the unresolved identifier issue.

---

@IBOutlet ...

// Add variables to be reachable for all methods    
var dosage : Int = 0
var kgs : Double = 0.0
var divisor : Double = 800.0 

@IBAction func dosagedesired(sender: UISlider) {

    // prepend self to variable as it is used
    self.dosage = Int(sender.value)
    dosagemg.text = "(self.dosage) mg"
    // adding the calculation here
    let result = self.kgs * Double(self.dosage) / self.divisor
    dripanswer.text = "(result)"
}

@IBAction func weightslider(sender: UISlider) {
    let weight = Int(sender.value)    
    // converts to kgs
    // the same here
    self.kgs = Int(sender.value) / Int(2.2)
    // adding the calculation here
    let result = self.kgs * Double(self.dosage) / self.divisor
    dripanswer.text = "(result)"
}

@IBAction func concentrationoption(sender: UISegmentedControl) {

    switch segmentoutlet.selectedSegmentIndex
    {
        case 0:                
            self.divisor = 800.0            
        case 1:
            self.divisor = 1600.0
        case 2:
            self.divisor = 3200.0
        default: 
            self.divisor = 800.0
    }
    // finally the calculation 
    let result = self.kgs * Double(self.dosage) / self.divisor
    dripanswer.text = "(result)"            
}

---

You should declare the variables kgs and dosage outside of any method ie at the class level, along with your outlets

//slider outlets
@IBOutlet weak var slider: UISlider!
@IBOutlet weak var sliderone: UISlider!
//segmentoutlet
@IBOutlet weak var segmentoutlet: UISegmentedControl!

//LABELS
//weight label
@IBOutlet weak var weightlabel: UILabel!
//dosage label
@IBOutlet weak var dosagemg: UILabel!
 //Drip Rate Answer Label
@IBOutlet weak var dripanswer: UILabel!

// You should declare the variables here:
var kgs = 0
var dosage = 0

And when you use kgs and dosage inside your methods, remove the word let because you're not declaring a variable.

The reason you do this is that you can't access variables declared in a method in another method. In the concentrationoption method, you can't access dosage , which is defined in dosagedesired method.

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