尝试使用选择器中选择的索引值而不是选择器的值

Question

I'm attempting to figure out how I can use the value of the index in my picker for an equation, rather than usng the selected number of the picker. I am not having success

Following is my array:

var wheelHeights = [5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70]

User, via picker, will select their preferred wheel height above the ground.

My code then goes through a few (a lot actually) if statement sections, and finally to my issue...

var wheelHeightFactor: Double {
    let wheelFactor = Double(wheelHeight)
    let densityWF = Double(densityWeightFactor)

      if wheelFactor <= 21 && densityWeightFactor >= 2.9 {
      let whf = Double((wheelFactor) * 0.2) + densityWeightFactor
             return whf

I'm looking to make wheelHeight in this equation be the picker index value, rather than the actual wheelHeight.

Following is what the code does now:

let whf = Double((15) * 0.2) + densityWeightFactor
             return whf

The equation SHOULD look like this in terms of where my numbers are if user selected 15:

let whf = Double((3) * 0.2) + densityWeightFactor
         return whf

Thank you all in advance

Answer 1

You will have to create a seperate @State variable to keep track of the actual index:
Consider the following example:

struct ContentView: View {
    let data = [1,5,10,20]
    @State private var selectedIndex = 0
    
    var body: some View {
        VStack {
            Text("Current index: \(selectedIndex)")
            
            Picker("Your Selection", selection: $selectedIndex) {
                ForEach(0..<data.count) { index in
                    Text("\(data[index])")
                }
            }
        }
    }
}

So if I understand your example right, then you want to use the actual index instead of wheelFactor . If so, you could do something like this:

@State private var selectedWheelHeightIndex = 0  
//...
let whf = Double((selectedWheelHeightIndex) * 0.2) + densityWeightFactor 
return whf

(I assume that you are using SwiftUI)...