Expenses

lib/data/models/static/currency_model.dart

@@ -120,6 +120,8 @@ abstract class CurrencyEntity extends Object
   @override
   double get listDisplayAmount => null;
 
+  
+
   static Serializer<CurrencyEntity> get serializer =>
       _$currencyEntitySerializer;
 }

lib/redux/app/app_state.dart

@@ -156,11 +156,15 @@ abstract class AppState implements Built<AppState, AppStateBuilder> {
 
   // STARTER: state getters - do not remove comment
   ExpenseState get expenseState => selectedCompanyState.expenseState;
+
   ListUIState get expenseListState => uiState.expenseUIState.listUIState;
+
   ExpenseUIState get expenseUIState => uiState.expenseUIState;
 
   VendorState get vendorState => selectedCompanyState.vendorState;
+
   ListUIState get vendorListState => uiState.vendorUIState.listUIState;
+
   VendorUIState get vendorUIState => uiState.vendorUIState;
 
   TaskState get taskState => selectedCompanyState.taskState;
@@ -191,6 +195,7 @@ abstract class AppState implements Built<AppState, AppStateBuilder> {
   String toString() {
     //return 'Is Loading: ${this.isLoading}, Invoice: ${this.invoiceUIState.selected}';
     //return 'Expense Categories: ${selectedCompany.expenseCategories}';
+    return 'Expense: ${uiState.expenseUIState.editing.expenseCurrencyId} - Invoice: ${uiState.expenseUIState.editing.invoiceCurrencyId}';
     return 'Route: ${uiState.currentRoute}';
   }
 }

lib/ui/expense/edit/expense_edit_settings.dart

@@ -8,6 +8,7 @@ import 'package:invoiceninja_flutter/utils/formatting.dart';
 import 'package:invoiceninja_flutter/utils/localization.dart';
 import 'package:invoiceninja_flutter/ui/app/form_card.dart';
 import 'package:invoiceninja_flutter/redux/static/static_selectors.dart';
+import 'package:invoiceninja_flutter/utils/money.dart';
 
 class ExpenseEditSettings extends StatefulWidget {
   const ExpenseEditSettings({
@@ -184,9 +185,17 @@ class ExpenseEditSettingsState extends State<ExpenseEditSettings> {
                         initialValue: staticState
                             .currencyMap[viewModel.expense.invoiceCurrencyId]
                             ?.name,
-                        onSelected: (SelectableEntity currency) =>
+                        onSelected: (SelectableEntity currency) {
-                            viewModel.onChanged(viewModel.expense.rebuild(
+                          final exchangeRate = getExchangeRate(context,
-                                (b) => b..invoiceCurrencyId = currency.id)),
+                              fromCurrencyId: expense.expenseCurrencyId,
+                              toCurrencyId: currency.id);
+                          viewModel.onChanged(expense.rebuild((b) => b
+                            ..invoiceCurrencyId = currency.id
+                            ..exchangeRate = exchangeRate));
+                          _exchangeRateController.text = formatNumber(
+                              exchangeRate, context,
+                              formatNumberType: FormatNumberType.input);
+                        },
                       ),
                       TextFormField(
                         controller: _exchangeRateController,

lib/utils/money.dart

@@ -0,0 +1,24 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_redux/flutter_redux.dart';
+import 'package:invoiceninja_flutter/constants.dart';
+import 'package:invoiceninja_flutter/redux/app/app_state.dart';
+
+double getExchangeRate(BuildContext context,
+    {int fromCurrencyId, int toCurrencyId}) {
+  final state = StoreProvider.of<AppState>(context).state;
+  final currencyMap = state.staticState.currencyMap;
+  final fromCurrency = currencyMap[fromCurrencyId];
+  final toCurrency = currencyMap[toCurrencyId];
+  // TODO replace with data from server
+  final baseCurrency = currencyMap[kCurrencyUSDollar];
+
+  if (fromCurrency == baseCurrency) {
+    return toCurrency.exchangeRate;
+  }
+
+  if (toCurrency == baseCurrency) {
+    return 1 / fromCurrency.exchangeRate;
+  }
+
+  return toCurrency.exchangeRate * (1 / fromCurrency.exchangeRate);
+}