How to modify a user input inside a SwiftUI form loop

Question

I'm developing a simple SwiftUI app in Xcode 11. I want to have a form that loops through multiple user input strings and displays a form with a button. When the user presses the button it modifies the input value - specifically increment or decrement it.

However when passing an array of references like UserInput().foo where UserInput is a published observable object I cannot modify the value inside a ForEach because the ForEach is passed a copy as oppose to the original reference (at least that's my basic understanding). How do I then try to achieve it? I read about inout and everybody says to avoid it but surely this must be a relatively common issue.

I've made an simple example of what I'm trying to do but I can't quite work it out:

import SwiftUI

class UserInput: ObservableObject {
    @Published var foo: String = ""
    @Published var bar: String = ""
}
struct ContentView: View {
    
    @ObservedObject var input = UserInput()
    
    var body: some View {
        LoopInputs()
    }
    func LoopInputs() -> AnyView?{
        
        var userinputs = [
            [UserInput().foo, "Foo"],
            [UserInput().bar, "Bar"]
        ]
        
        var inputs: some View{
            VStack(){
                ForEach(userinputs, id: \.self){userinput in
                    Text("\(userinput[1]): \(String(userinput[0]))")
                    Button(action: {
                        increment(input: String(userinput[0]))
                    }){
                        Text("Increase")
                    }
                }
            }
        }
        
        return AnyView(inputs)
    }
    func increment(input: String){
        var lead = Int(input) ?? 0
        lead += 1
        //    input = String(lead)
    }
}

I can't catch sense of this snapshot, it does not operate with var input at all. Would you elaborate more? — Asperi
– Asperi, Commented Jul 4, 2020 at 9:03

SwiftyJoeyy · Accepted Answer · 2022-06-03 08:31:52Z

As I understood, when adding a value to userinputs, the ForEach values doesn't change. Well, if that's the case, first of all, you could try creating a struct and in it, you declare foo and bar, then just declare a variable of type the struct. It'll look like this:

struct Input: Identifiable {
    var id = UUID()
    var foo: String
    var bar: String
}
class UserInput: ObservableObject {
    @Published var inputs: [Input] = [Input]()
}
//ContentView
struct ContentView: View {
    @ObservedObject var input = UserInput()
    var body: some View {
        LoopInputs()
    }
    func LoopInputs() -> AnyView? {
        var inputs: some View {
            VStack {
                ForEach(input.inputs) { userinput in
                    Text("\(userinput.bar): \(String(userinput.foo))")
                    Button(action: {
                        increment(input: String(userinput.foo))
                    }) {
                        Text("Increase")
                    }
                }
            }
        }
        return AnyView(inputs)
    }
    func increment(input: String) {
        var lead = Int(input) ?? 0
        lead += 1
    //    input = String(lead)
    }
}

Wouldn't this be easier and more elegant?

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