Работает функционал переключения валют, остались правки по ui

lib/screens/purchase.dart

@@ -203,29 +203,31 @@ class PurchaseScreenState<T> extends BaseState<PurchaseScreen> {
 
           String url = user['purchases_url'];
 
-          var body = {
-            'doc_id': result,
-            'curr_iso_code': '643',
-            'commit': 'true',
-            'sum_total': sumTotal
-          };
+          helper.getCurrency().then((currency) {
+            var body = {
+              'doc_id': result,
+              'curr_iso_code': currency.toString(),
+              'commit': 'true',
+              'sum_total': sumTotal
+            };
 
-          var headers = {
-            'DM-Authorization': 'dmapptoken $appToken',
-            'Authorization': 'dmtoken ${token}'
-          };
+            var headers = {
+              'DM-Authorization': 'dmapptoken $appToken',
+              'Authorization': 'dmtoken ${token}'
+            };
 
-          httpClient.post(url, body: body, headers: headers).then((response) {
+            httpClient.post(url, body: body, headers: headers).then((response) {
 
-            print(response.body);
-            helper.close().then((_) {
-              Navigator.of(context).pop();
-              pushRouteReplacement(context, new PurchaseSuccessScreen(sumTotal, user['first_name'] == null ? '' : user['first_name']));
+              print(response.body);
+              helper.close().then((_) {
+                Navigator.of(context).pop();
+                pushRouteReplacement(context, new PurchaseSuccessScreen(sumTotal, user['first_name'] == null ? '' : user['first_name']));
+              });
+
+            }).catchError((error) {
+              purchaseInProgress = false;
+              print(error.toString());
             });
-
-          }).catchError((error) {
-            purchaseInProgress = false;
-            print(error.toString());
           });
         });
       }