Managable currency symbol indication

README.md

@@ -19,8 +19,6 @@ Drop a `NumberEditingTextController` into any `TextField`. The user sees formatt
 - Allows custom separators for grouping and decimal characters
 - Lets you change locale, currency, separators, and precision at runtime
 
-![number_editing_controller demo](https://raw.githubusercontent.com/nerdy-pro/flutter_number_editing_controller/main/img/screenshot.gif)
-
 ## Installation
 
 ```shell
@@ -56,6 +54,8 @@ final amount = controller.number; // e.g. 1234.56
 
 Formats whole numbers with grouping separators.
 
+![Integer formatting demo](https://raw.githubusercontent.com/nerdy-pro/flutter_number_editing_controller/main/img/integer.gif)
+
 ```dart
 final controller = NumberEditingTextController.integer(locale: 'en');
 // User types "1000000" -> displays "1,000,000"
@@ -65,6 +65,8 @@ final controller = NumberEditingTextController.integer(locale: 'en');
 
 Formats numbers with a decimal part. Control minimum and maximum fraction digits.
 
+![Decimal formatting demo](https://raw.githubusercontent.com/nerdy-pro/flutter_number_editing_controller/main/img/decimal.gif)
+
 ```dart
 final controller = NumberEditingTextController.decimal(
   locale: 'en',
@@ -78,6 +80,8 @@ final controller = NumberEditingTextController.decimal(
 
 Formats monetary amounts with a currency symbol placed according to locale rules.
 
+![Currency formatting demo](https://raw.githubusercontent.com/nerdy-pro/flutter_number_editing_controller/main/img/currency.gif)
+
 ```dart
 final controller = NumberEditingTextController.currency(
   currencyName: 'EUR',
@@ -108,6 +112,14 @@ Available on `CurrencyEditingController` and `NumberEditingTextController.curren
 | `currencyName` | `String?` | From locale | ISO 4217 currency code (e.g. `'USD'`, `'EUR'`, `'JPY'`). |
 | `currencySymbol` | `String?` | From currency code | Custom currency symbol (e.g. `'$'`, `'€'`, `'₺'`). |
 | `decimalSeparator` | `String?` | From locale | Symbol used to separate the decimal part. |
+| `showCurrencySymbol` | `bool` | `true` | Whether to include the currency symbol in the formatted text. Set to `false` when displaying the symbol outside the text field. |
+
+`CurrencyEditingController` also exposes these read-only properties:
+
+| Property | Type | Description |
+|----------|------|-------------|
+| `resolvedCurrencySymbol` | `String` | The actual symbol used for formatting, resolved from `currencySymbol` or `currencyName` + `locale`. |
+| `currencySymbolPosition` | `CurrencySymbolPosition` | Whether the symbol is a `.prefix` or `.suffix` in the current locale. |
 
 ### Decimal parameters
 
@@ -160,12 +172,41 @@ final decimal = DecimalEditingController(
 decimal.maximumFractionDigits = 2; // Only available on DecimalEditingController
 ```
 
+### Displaying the currency symbol outside the text field
+
+Use `showCurrencySymbol: false` to hide the symbol from the formatted text, then display it as a prefix or suffix decoration on the `TextField`. The `resolvedCurrencySymbol` and `currencySymbolPosition` properties tell you what to display and where.
+
+![Currency prefix/suffix demo](https://raw.githubusercontent.com/nerdy-pro/flutter_number_editing_controller/main/img/currency-prefix.gif)
+
+```dart
+final controller = CurrencyEditingController(
+  currencyName: 'USD',
+  locale: 'en',
+  showCurrencySymbol: false,
+);
+
+TextField(
+  controller: controller,
+  decoration: InputDecoration(
+    prefixText: controller.currencySymbolPosition == CurrencySymbolPosition.prefix
+        ? controller.resolvedCurrencySymbol
+        : null,
+    suffixText: controller.currencySymbolPosition == CurrencySymbolPosition.suffix
+        ? controller.resolvedCurrencySymbol
+        : null,
+  ),
+)
+// User types "1234" -> field shows "$" as prefix + "1,234" as text
+```
+
+This is useful when you want the symbol to remain fixed and not shift as the user types, or when you need custom styling for the symbol.
+
 ## Class hierarchy
 
 | Class | Description |
 |-------|-------------|
 | `NumberEditingTextController` | Interface. Use the factory constructors or program against this type. |
-| `CurrencyEditingController` | Formats currency amounts. Mutable: `currencyName`, `currencySymbol`, `decimalSeparator`. |
+| `CurrencyEditingController` | Formats currency amounts. Mutable: `currencyName`, `currencySymbol`, `decimalSeparator`, `showCurrencySymbol`. Read-only: `resolvedCurrencySymbol`, `currencySymbolPosition`. |
 | `DecimalEditingController` | Formats decimal numbers. Mutable: `minimalFractionDigits`, `maximumFractionDigits`, `decimalSeparator`. |
 | `IntegerEditingController` | Formats integers. No type-specific options beyond the shared ones. |
 
@@ -225,4 +266,4 @@ void dispose() {
 
 ## Example app
 
-A working example app with currency picker, locale switcher, and negative toggle is available in the [example](https://github.com/nerdy-pro/flutter_number_editing_controller/tree/main/example) directory.
+A working example app is available in the [example](https://github.com/nerdy-pro/flutter_number_editing_controller/tree/main/example) directory. It demonstrates currency picker, locale switcher, negative toggle, and external currency symbol placement with prefix/suffix decoration.

example/lib/main.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:number_editing_controller_example/variants/currency_input.dart';
 import 'package:number_editing_controller_example/variants/decimal_input.dart';
+import 'package:number_editing_controller_example/variants/external_symbol_input.dart';
 import 'package:number_editing_controller_example/variants/integer_input.dart';
 
 void main() {
@@ -29,7 +30,7 @@ class HomePage extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return DefaultTabController(
-      length: 3,
+      length: 4,
       child: Scaffold(
         appBar: AppBar(
           backgroundColor: Theme.of(context).colorScheme.inversePrimary,
@@ -39,6 +40,7 @@ class HomePage extends StatelessWidget {
               Tab(text: 'Currency'),
               Tab(text: 'Integer'),
               Tab(text: 'Decimal'),
+              Tab(text: 'Prefix/Suffix'),
             ],
           ),
         ),
@@ -47,6 +49,7 @@ class HomePage extends StatelessWidget {
             CurrencyInput(),
             IntegerInput(),
             DecimalInput(),
+            ExternalSymbolInput(),
           ],
         ),
       ),

example/lib/variants/external_symbol_input.dart

@@ -0,0 +1,91 @@
+import 'package:flutter/material.dart';
+import 'package:number_editing_controller/number_editing_controller.dart';
+
+class ExternalSymbolInput extends StatefulWidget {
+  const ExternalSymbolInput({super.key});
+
+  @override
+  State<ExternalSymbolInput> createState() => _ExternalSymbolInputState();
+}
+
+class _ExternalSymbolInputState extends State<ExternalSymbolInput> {
+  final _controller = CurrencyEditingController(
+    locale: 'en',
+    showCurrencySymbol: false,
+  );
+
+  String _selectedLocale = 'en';
+
+  static const _locales = ['en', 'de', 'fr', 'ja', 'ru'];
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final isPrefix = _controller.currencySymbolPosition ==
+        CurrencySymbolPosition.prefix;
+
+    return Center(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            DropdownButton<String>(
+              value: _selectedLocale,
+              items: _locales
+                  .map((l) => DropdownMenuItem(value: l, child: Text(l)))
+                  .toList(),
+              onChanged: (value) {
+                if (value == null) return;
+                setState(() {
+                  _selectedLocale = value;
+                  _controller.locale = value;
+                });
+              },
+            ),
+            const SizedBox(height: 8),
+            Text(
+              'Symbol: ${_controller.resolvedCurrencySymbol}'
+              '  Position: ${_controller.currencySymbolPosition.name}',
+              style: Theme.of(context).textTheme.bodySmall,
+            ),
+            const SizedBox(height: 16),
+            const Text('You have entered:'),
+            ValueListenableBuilder(
+              valueListenable: _controller,
+              builder: (context, value, child) {
+                return Text(
+                  '${_controller.number ?? 0}',
+                  style: Theme.of(context).textTheme.headlineMedium,
+                );
+              },
+            ),
+            const SizedBox(height: 16),
+            TextField(
+              textAlign: TextAlign.center,
+              keyboardType: const TextInputType.numberWithOptions(
+                decimal: true,
+                signed: true,
+              ),
+              controller: _controller,
+              decoration: InputDecoration(
+                prefixText: isPrefix
+                    ? _controller.resolvedCurrencySymbol
+                    : null,
+                suffixText: isPrefix
+                    ? null
+                    : _controller.resolvedCurrencySymbol,
+                border: const OutlineInputBorder(),
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}

lib/number_editing_controller.dart

@@ -2,6 +2,7 @@
 /// as you type with locale support.
 library;
 
+export 'src/parsed_number_format.dart' show CurrencySymbolPosition;
 export 'src/text_controller.dart'
     show
         NumberEditingTextController,

lib/src/parsed_number_format.dart

@@ -6,6 +6,15 @@ import 'package:number_editing_controller/src/grouping.dart';
 import 'package:number_editing_controller/src/mask_parser_iterator.dart';
 import 'package:number_editing_controller/src/parts.dart';
 
+/// Whether the currency symbol is placed before or after the number.
+enum CurrencySymbolPosition {
+  /// The symbol appears before the number (e.g. `$100`).
+  prefix,
+
+  /// The symbol appears after the number (e.g. `100 €`).
+  suffix,
+}
+
 /// The result of formatting a [TextEditingValue] through [ParsedNumberFormat].
 class FormatResult {
   /// The formatted text editing value.
@@ -47,6 +56,7 @@ class ParsedNumberFormat {
     String? decimalSeparator,
     String? groupSeparator,
     bool allowNegative = true,
+    bool showCurrencySymbol = true,
   }) {
     final currentLocale = _verifiedLocale(locale, NumberFormat.localeExists)!;
     final symbols = numberFormatSymbols[currentLocale] as NumberSymbols;
@@ -62,6 +72,7 @@ class ParsedNumberFormat {
       decimalSeparator: decimalSeparator,
       groupSeparator: groupSeparator,
       allowNegative: allowNegative,
+      showCurrencySymbol: showCurrencySymbol,
     );
   }
 
@@ -121,6 +132,7 @@ class ParsedNumberFormat {
     String? decimalSeparator,
     String? groupSeparator,
     required bool allowNegative,
+    bool showCurrencySymbol = true,
   }) {
     final currencyCode = currencyName ?? symbols.DEF_CURRENCY_CODE;
     final format = NumberFormat(mask);
@@ -129,7 +141,7 @@ class ParsedNumberFormat {
     final min = minimalFractionDigits ?? format.minimumFractionDigits;
     final max = maximumFractionDigits ?? format.maximumFractionDigits;
 
-    final parts = mask.getNumberFormatParts(
+    var parts = mask.getNumberFormatParts(
       minDecimalPart: min,
       maxDecimalPart: max,
       currencySign: resolvedCurrencySymbol,
@@ -138,11 +150,49 @@ class ParsedNumberFormat {
       allowNegative: allowNegative,
     );
 
+    if (!showCurrencySymbol) {
+      parts = parts.where((p) => p is! StaticPart).toList();
+    }
+
     return ParsedNumberFormat._(parts, allowNegative);
   }
 
   ParsedNumberFormat._(this.parts, this._allowNegative);
 
+  /// Resolves the currency symbol for the given parameters.
+  static String resolvedSymbol({
+    String? locale,
+    String? currencyName,
+    String? currencySymbol,
+  }) {
+    if (currencySymbol != null) {
+      return currencySymbol;
+    }
+    final currentLocale = _verifiedLocale(locale, NumberFormat.localeExists)!;
+    final symbols = numberFormatSymbols[currentLocale] as NumberSymbols;
+    final currencyCode = currencyName ?? symbols.DEF_CURRENCY_CODE;
+    final format = NumberFormat(symbols.CURRENCY_PATTERN);
+    return format.simpleCurrencySymbol(currencyCode);
+  }
+
+  /// Determines whether the currency symbol is a prefix or suffix
+  /// for the given locale.
+  static CurrencySymbolPosition symbolPosition({String? locale}) {
+    final currentLocale = _verifiedLocale(locale, NumberFormat.localeExists)!;
+    final symbols = numberFormatSymbols[currentLocale] as NumberSymbols;
+    final pattern = symbols.CURRENCY_PATTERN;
+    // In ICU patterns, \u00A4 is the currency placeholder.
+    // If it appears before the first digit placeholder, it's a prefix.
+    final currencyIndex = pattern.indexOf('\u00A4');
+    final digitIndex = pattern.indexOf(RegExp('[0#]'));
+    if (currencyIndex < 0) {
+      return CurrencySymbolPosition.prefix;
+    }
+    return currencyIndex < digitIndex
+        ? CurrencySymbolPosition.prefix
+        : CurrencySymbolPosition.suffix;
+  }
+
   FormatResult formatValue(TextEditingValue textEditingValue) {
     var result = textEditingValue;
     var charPosition = 0;

lib/src/text_controller.dart

@@ -194,6 +194,7 @@ class CurrencyEditingController extends TextEditingController
   String? _currencyName;
   String? _currencySymbol;
   String? _decimalSeparator;
+  bool _showCurrencySymbol;
 
   @override
   late ParsedNumberFormat _format;
@@ -207,9 +208,11 @@ class CurrencyEditingController extends TextEditingController
     String? decimalSeparator,
     String? groupSeparator,
     bool allowNegative = true,
+    bool showCurrencySymbol = true,
   })  : _currencyName = currencyName,
         _currencySymbol = currencySymbol,
-        _decimalSeparator = decimalSeparator {
+        _decimalSeparator = decimalSeparator,
+        _showCurrencySymbol = showCurrencySymbol {
     _locale = locale;
     _groupSeparator = groupSeparator;
     _allowNegative = allowNegative;
@@ -253,6 +256,37 @@ class CurrencyEditingController extends TextEditingController
     _rebuildFormat();
   }
 
+  /// Whether the currency symbol is shown in the formatted text.
+  ///
+  /// When `false`, the currency symbol and its separator are hidden.
+  /// This is useful when the symbol is displayed as a prefix or suffix
+  /// widget outside the text field.
+  ///
+  /// Defaults to `true`.
+  bool get showCurrencySymbol => _showCurrencySymbol;
+  set showCurrencySymbol(bool value) {
+    if (_showCurrencySymbol == value) {
+      return;
+    }
+    _showCurrencySymbol = value;
+    _rebuildFormat();
+  }
+
+  /// The resolved currency symbol used for formatting.
+  ///
+  /// Returns the custom [currencySymbol] if set, otherwise the symbol
+  /// derived from [currencyName] and [locale].
+  String get resolvedCurrencySymbol => ParsedNumberFormat.resolvedSymbol(
+        locale: _locale,
+        currencyName: _currencyName,
+        currencySymbol: _currencySymbol,
+      );
+
+  /// Whether the currency symbol is placed before or after the number
+  /// in the current locale.
+  CurrencySymbolPosition get currencySymbolPosition =>
+      ParsedNumberFormat.symbolPosition(locale: _locale);
+
   @override
   ParsedNumberFormat _buildFormat() => ParsedNumberFormat.currency(
         locale: _locale,
@@ -261,6 +295,7 @@ class CurrencyEditingController extends TextEditingController
         decimalSeparator: _decimalSeparator,
         groupSeparator: _groupSeparator,
         allowNegative: _allowNegative,
+        showCurrencySymbol: _showCurrencySymbol,
       );
 }