TextField clean button for inputs of type <Double> in SwiftUI

Question

Could you please help me with clear button code, that doesn't work properly?

I have a TextField, which stores an input of type Double, and unfortunately the classic solution of including additional modifier is not working.

Here is my code:

import SwiftUI

struct ContentView: View {
    
    @State private var amount: Double = 10
    @FocusState private var isFocused: Bool
    
    var body: some View {
        NavigationView {
            Form {
                Section {
                    TextField("Amount to pay", value: $amount, format: .currency(code: "USD"))
                        .keyboardType(.decimalPad)
                        .focused($isFocused)
                        .modifier(TextFieldClearButton(amount: $amount, focus: $isFocused))
                }
            }
        }
        .toolbar {
            ToolbarItemGroup(placement: .keyboard) {
                
                Spacer()
                
                Button("Done") {
                    isFocused = false
                }
            }
        }
    }
}

struct TextFieldClearButton: ViewModifier {
    @Binding var amount: Double
    @FocusState.Binding var focus: Bool
    
    func body(content: Content) -> some View {
        HStack {
            content
            
            if amount != 0.0 {
                Button(
                    action: {
                        self.amount = 0.0
                        if focus == false {
                            focus = true
                        }
                    },
                    label: {
                        Image(systemName: "delete.left")
                            .foregroundColor(Color(UIColor.opaqueSeparator))
                    }
                )
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Looks like the view is not updated when I am calling the modifier, so I can see only default value. How can I fix this?

Does this answer your question stackoverflow.com/a/72219757/12299030? — Asperi
– Asperi, Commented May 20, 2022 at 12:35

Yrb · Accepted Answer · 2022-05-21 15:03:22Z

I have found that while a TextField is focused, you can't externally update the value. It simply ignores it. So, in order to get the Textfield to update while focused, you have to cause a view refresh as well. The simplest way of doing this is to put a .id() on the TextField with a value you can change like this:

struct ButtonClearTextField: View {
    // Your Double is now optional
    @State private var amount: Double? = 10
    @FocusState private var isFocused: Bool
    @State var updater = UUID()
    
    var body: some View {
        Form {
            Section {
                TextField("Amount to pay", value: $amount, format: .currency(code: "USD"))
                    .keyboardType(.decimalPad)
                    .focused($isFocused)
                    // Put the id in the view. I put it here as it helps indicate what is changing.
                    .id(updater)
                    // textFieldClearButton is a func on View as a result of the extension
                    .textFieldClearButton(amount: $amount, focus: $isFocused, updater: $updater)

                // I added this button so you could test that if
                // the TextField is focused it won't change.
                Button {
                    amount = 0
                } label: {
                    Text("Clear")
                }
                
            }
        }
        .toolbar {
            ToolbarItemGroup(placement: .keyboard) {
                
                Spacer()
                
                Button("Done") {
                    isFocused = false
                }
            }
        }
    }
}

struct TextFieldClearButton: ViewModifier {
    @Binding var amount: Double?
    @FocusState.Binding var focus: Bool
    @Binding var updater: UUID
    
    func body(content: Content) -> some View {
        HStack {
            content
            
            if amount != 0.0 {
                Button(
                    action: {
                        // Setting to nil clears the field
                        amount = nil
                        // After setting the value, 
                        updater = UUID()
                        DispatchQueue.main.async {
                            focus = true
                        }
                    },
                    label: {
                        Image(systemName: "delete.left")
                            .foregroundColor(Color(UIColor.opaqueSeparator))
                    }
                )
            }
        }
    }
}

// Creates func textFieldClearButton
extension View {
    func textFieldClearButton(amount: Binding<Double?>, focus: FocusState<Bool>.Binding, updater: Binding<UUID>) -> some View {
        self.modifier(TextFieldClearButton(amount: amount, focus: focus, updater: updater))
    }
}

In order to get the behavior that Asperi linked to, you simply need to use an optional value and set it to nil.

I also made a View extension to clean up the code at the call site a bit.

Hello. Very useful solution, that solves my problem, I need to study more about using UUID(). However I have one issue - I guess that keyboard FocusState should be TRUE after user clicks on clear button. Now it doesn't work properly, actually your focus = true in Button action does not set the focus to TRUE, it remains FALSE. Unfortunately I have no idea, why this piece of code could not toggle the value of focus to TRUE.
I updated the code to add a DispatchQueue around the focus = true. The problem was a timing issue. When the updater changes, the view refreshes and without the DispatchQueue to slow things a bit, isFocused was being set to true, and then the view refresh was setting it back to false.

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