OptionalTextField.swift

OptionalTextField.swift

//
//  OptionalTextField.swift
//
//
//  Created by Daniel Lyons on 2024-08-12.
//

import Foundation
import SwiftUI

/// A `TextField` with a `Toggle` which allows the user to include or remove the `TextField`.
///
/// If the user sets the `Toggle` to `false` then the `TextField` will be replaced with the `noTextFieldView`
/// and the `optionalString` will be set to `nil`.
@available(iOS 15.0, macOS 12.0, *)
public struct OptionalTextField<AddTextFieldLabel: View, RemoveTextFieldLabel: View>: View {
  @Binding var optionalString: String?
  @State private var hasString: Bool
  /// a string to assign to ``optionalString`` if ever the user toggles the string off and then on again
  ///
  /// This cache will only live as long as the View
  @State private var cachedString: String
  let titleKey: LocalizedStringKey
  // the label of the add text field button
  let addTextFieldLabel: AddTextFieldLabel
  // the label of the remove text field button
  let removeTextFieldLabel: RemoveTextFieldLabel
  let prompt: Text?
  
  /// Creates an OptionalTextField
  ///
  /// >Note: `prompt` will be ignored pre-iOS 15 and macOS 12
  public init(
    _ titleKey: LocalizedStringKey,
    text optionalString: Binding<String?>,
    prompt: Text? = nil,
    @ViewBuilder addTextFieldLabel: () -> AddTextFieldLabel,
    @ViewBuilder removeTextFieldLabel: () -> RemoveTextFieldLabel
  ) {
    self.titleKey = titleKey
    self._optionalString = optionalString
    self.prompt = prompt
    self.cachedString = optionalString.wrappedValue ?? ""
    self.hasString = optionalString.wrappedValue != nil
    self.addTextFieldLabel = addTextFieldLabel()
    self.removeTextFieldLabel = removeTextFieldLabel()
  }
  
  @FocusState var isFocusedOnTextField: Bool
  
  public var body: some View {
    Group {
      
      if let string = optionalString {
        if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
          HStack {
            Button {
              withAnimation {
                isFocusedOnTextField = false // we must remove the focus first, otherwise the focus will be on the TextField, which will write to the String which will cause optionalString to not be nil
                hasString = false
              }
            } label: {
              removeTextFieldLabel
            }
            
            TextField(
              titleKey,
              text: $optionalString.toNonOptional(defaultValue: string), // it should not be possible for this default value to ever be used
              prompt: prompt
            )
            .focused($isFocusedOnTextField)
          }
          .buttonStyle(.plain)
        } else {
          TextField(
            titleKey,
            text: $optionalString.toNonOptional(defaultValue: string) // it should not be possible for this default value to ever be used
          )
        }
      } else {
        Button {
          withAnimation {
            isFocusedOnTextField = true
            hasString = true
          }
        } label: {
          addTextFieldLabel
        }
      }
    }
    .onChange(of: hasString) { newValue in
      optionalString = if newValue { cachedString } else { nil }
    }
    .onChange(of: optionalString) { newValue in
      guard let newValue else {
        return
      }
      cachedString = newValue
    }
  }
}

@available(iOS 15.0, macOS 12.0, *)
struct OptionalTextFieldPreview: View {
  @State var string: String? = "DandyLyons"
  
  var body: some View {
    OptionalTextField(
      "Nickname",
      text: $string.animation(),
      addTextFieldLabel: {
        Label("Add Nickname", systemImage: "plus.circle.fill")
      },
      removeTextFieldLabel: {
        Label("Remove Nickname", systemImage: "minus.circle.fill")
          .labelStyle(.iconOnly)
      }
    )
  }
}

#Preview {
  Form {
    if #available(iOS 15.0, macOS 12.0, *) {
      OptionalTextFieldPreview()
    } else {
      // Fallback on earlier versions
    }
  }
}

@available(iOS 15.0, macOS 12.0, *)
extension OptionalTextField where AddTextFieldLabel == Text, RemoveTextFieldLabel == Text {
  public init(
    _ titleKey: LocalizedStringKey,
    text optionalString: Binding<String?>,
    prompt: LocalizedStringKey,
    addTextField: LocalizedStringKey,
    removeTextField: LocalizedStringKey
  ) {
    self.titleKey = titleKey
    self._optionalString = optionalString
    self.cachedString = optionalString.wrappedValue ?? ""
    self.hasString = optionalString.wrappedValue != nil
    self.prompt = Text(prompt)
    self.addTextFieldLabel = Text(addTextField)
    self.removeTextFieldLabel = Text(removeTextField)
  }
}