OnChangeContentView.swift

import SwiftUI

struct ContentView: View {
  @State var value1 = Double()
  @State var value2 = Double()
  @State var total = Double()
  
  func addValues() {
    total = value1 + value2
  }
  
  var body: some View {
    VStack {
      Slider(value: $value1, in: 0...100,
             minimumValueLabel: Text("0"),
             maximumValueLabel: Text("100")) {
        Text("Value 1")
      }
      .onChange(of: value1) {
        _ in addValues()
      }
      Slider(value: $value2, in: 0...100,
             minimumValueLabel: Text("0"),
             maximumValueLabel: Text("100")) {
        Text("Value 2")
      }
      .onChange(of: value2) {
        _ in addValues()
      }
      Text("Total: \(total)")
    }
  }
}