SwiftUI Picker VALUE

Question

I've been trying to program something with swiftui recently, it's difficult, how can I transfer the value of the picker into the text field, I'm desperate!

and why can I not work with the value $ khValue directly as in the text field?

I've already spent hours searching the internet… I haven't found anything yet, swiftUI is completely different from swift

import SwiftUI

struct KH_aus_Co2: View {
    @State private var kh_Picker : String = ""
    @State private var ph_Picker: String = ""
    
    
    
    var kh_vol = [Int](0..<21)
    var ph_vol = [Int](0..<10)
    
    init(){
        UITableView.appearance().backgroundColor = .clear
    }
    
    @State private var khWert: String = ""
    @State private var phWert: String = ""
    @State private var phco2Wert: String = ""
    
    
    
    var calculation: String {
        
        guard khWert.isEmpty == false, phWert.isEmpty == false else { return "" }
        
        
        guard let kh = Double(khWert), let ph  = Double(phWert) else { return "Error" }
        
        let product = kh/2.8 * pow(10,7.90-ph)
        
        
        return String(format: "%.2f", product)
    }
    
    
    
    var body: some View {
        
        VStack() {
            Text("Co2 = \(calculation) mg/ltr")
                
                .font(.largeTitle)
                .multilineTextAlignment(.center)
                .foregroundColor(Color.green)
                .frame(width: 300, height: 60, alignment: .center)
                .border(Color.green)
                .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity, alignment: .center)
            
            
            
            HStack {
                
                
                TextField("KH Wert", text: $khWert)
                    .border(Color.green)
                    .frame(width: 120, height: 70, alignment: .center)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    //                            .textContentType(.oneTimeCode)
                    .keyboardType(.numberPad)
                
                TextField("PH Wert", text: $phWert)
                    .border(Color.green)
                    .frame(width: 120, height: 70, alignment: .center)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    //                            .textContentType(.oneTimeCode)
                    .keyboardType(.numberPad)
                
            }
            
            GeometryReader { geometry in
                HStack {
                    
                    Picker(selection: self.$kh_Picker, label: Text("")) {
                        ForEach(0 ..< self.kh_vol.count) { index in
                            Text("\(self.kh_vol[index])").tag(index)
                            //
                        }
                        
                    }
                    .frame(width: geometry.size.width/3, height: 100, alignment: .center) .clipped()
                    
                    Picker(selection: self.$ph_Picker, label: Text("")) {
                        ForEach(0 ..< self.ph_vol.count) { index in
                            Text("\(self.ph_vol[index])").tag(index)
                        }
                        
                    }
                    .frame(width: geometry.size.width/3, height: 100, alignment: .center) .clipped()
                    
                    
                }
            }
            
        }
            
            
        .navigationBarTitle(Text("Co2 aus KH & PH"))
        .font(/*@START_MENU_TOKEN@*/.title/*@END_MENU_TOKEN@*/)
        
        
    }
    
    
    
}

struct KH_aus_Co2_Previews: PreviewProvider {
    static var previews: some View {
        Co2_aus_KH()
        
    }
}

big thanks for your help

Jürgen....................................

Answer 1

If I understand you correctly, you want the pickers to update the values in the textfields. If so, then you want to bind the same value to the picker that the textfield is using. Since that value is a String, you will want to use String values in your picker.

Use .map(String.init) to turn the kh_vol and ph_vol ranges into arrays of String, and use \.self as the id::

Picker(selection: self.$khWert, label: Text("")) {
    ForEach(self.kh_vol.map(String.init), id: \.self) { index in
        Text(index)
    }
    
}
.frame(width: geometry.size.width/3, height: 100, alignment: .center)
.clipped()

Picker(selection: self.$phWert, label: Text("")) {
    ForEach(self.ph_vol.map(String.init), id: \.self) { index in
        Text(index)
    }
    
}
.frame(width: geometry.size.width/3, height: 100, alignment: .center)
.clipped()