未处理的异常：“String”类型不是“num”类型的子类型

Question

大家好，我有一个用户应用程序和管理应用程序，在用户应用程序中我提供了一个名为 promocode 的选项，为此我在数据库中创建了 2 个促销代码。当我应用它们时它工作正常，但是当我添加一个新的来自管理应用程序的促销代码出现错误。有人可以帮助我。

这是我的代码：

if (passengers != null && passengers != 0) {
      total = ticketprice * passengers;
    }
    if (promoCode != null && promoCode.isNotEmpty) {
      _firestore
          .collection('promo_codes')
          .where('promo_code', isEqualTo: promoCode)
          .getDocuments()
          .then((QuerySnapshot data) {
        if (data != null && data.documents.length > 0) {
          var documentData = data.documents[0];

          if (documentData['price_reduction'] != null) {
            setState(() {
              total -= int.parse(documentData['price_reduction']);
            });
          } else if (documentData['percentage_reduction'] != null) {
            setState(() {
              total -= (total * int.parse(documentData['percentage_reduction']));
            });
          }

          setState(() {
            grandTotal = total;
          });
        }
      });
    }

我只添加了促销代码的主要代码，如果有人想通过它，我会分享整个代码。

这是我的错误：

════════ Exception caught by foundation library ════════════════════════════════════════════════════
The following FormatException was thrown while dispatching notifications for TextEditingController:
Invalid number (at character 1)

^

When the exception was thrown, this was the stack: 
#0      int._throwFormatException (dart:core-patch/integers_patch.dart:131:7)
#1      int.parse (dart:core-patch/integers_patch.dart:55:14)
#2      _MyAppState.testListener.<anonymous closure> (package:fire/main.dart:136:24)
#3      State.setState (package:flutter/src/widgets/framework.dart:1148:30)
#4      _MyAppState.testListener (package:fire/main.dart:130:5)
...
The TextEditingController sending notification was: TextEditingController#1dc24(TextEditingValue(text: ┤├, selection: TextSelection(baseOffset: 0, extentOffset: 0, affinity: TextAffinity.downstream, isDirectional: false), composing: TextRange(start: -1, end: -1)))
════════════════════════════════════════════════════════════════════════════════════════════════════
E/flutter (14220): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'String' is not a subtype of type 'num'
E/flutter (14220): #0      _MyAppState._onChanged.<anonymous closure>.<anonymous closure> (package:fire/main.dart:109:36)
E/flutter (14220): #1      State.setState (package:flutter/src/widgets/framework.dart:1148:30)
E/flutter (14220): #2      _MyAppState._onChanged.<anonymous closure> (package:fire/main.dart:108:13)
E/flutter (14220): #3      _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter (14220): #4      _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter (14220): #5      _FutureListener.handleValue (dart:async/future_impl.dart:140:18)
E/flutter (14220): #6      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:682:45)
E/flutter (14220): #7      Future._propagateToListeners (dart:async/future_impl.dart:711:32)
E/flutter (14220): #8      Future._completeWithValue (dart:async/future_impl.dart:526:5)
E/flutter (14220): #9      _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:33:15)
E/flutter (14220): #10     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:291:13)
E/flutter (14220): #11     Query.getDocuments (package:cloud_firestore/src/query.dart)
E/flutter (14220): <asynchronous suspension>
E/flutter (14220): #12     _MyAppState._onChanged (package:fire/main.dart:102:12)
E/flutter (14220): #13     _MyAppState.build.<anonymous closure> (package:fire/main.dart:559:33)
E/flutter (14220): #14     EditableTextState._formatAndSetValue (package:flutter/src/widgets/editable_text.dart:1607:14)
E/flutter (14220): #15     EditableTextState.updateEditingValue (package:flutter/src/widgets/editable_text.dart:1208:5)
E/flutter (14220): #16     TextInput._handleTextInputInvocation (package:flutter/src/services/text_input.dart:962:36)
E/flutter (14220): #17     MethodChannel._handleAsMethodCall (package:flutter/src/services/platform_channel.dart:402:55)
E/flutter (14220): #18     MethodChannel.setMethodCallHandler.<anonymous closure> (package:flutter/src/services/platform_channel.dart:370:54)
E/flutter (14220): #19     _DefaultBinaryMessenger.handlePlatformMessage (package:flutter/src/services/binding.dart:200:33)
E/flutter (14220): #20     _invoke3.<anonymous closure> (dart:ui/hooks.dart:303:15)
E/flutter (14220): #21     _rootRun (dart:async/zone.dart:1126:13)
E/flutter (14220): #22     _CustomZone.run (dart:async/zone.dart:1023:19)
E/flutter (14220): #23     _CustomZone.runGuarded (dart:async/zone.dart:925:7)
E/flutter (14220): #24     _invoke3 (dart:ui/hooks.dart:302:10)
E/flutter (14220): #25     _dispatchPlatformMessage (dart:ui/hooks.dart:162:5)
E/flutter (14220): 
E/flutter (14220): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'String' is not a subtype of type 'num'
E/flutter (14220): #0      _MyAppState._onChanged.<anonymous closure>.<anonymous closure> (package:fire/main.dart:109:36)
E/flutter (14220): #1      State.setState (package:flutter/src/widgets/framework.dart:1148:30)
E/flutter (14220): #2      _MyAppState._onChanged.<anonymous closure> (package:fire/main.dart:108:13)
E/flutter (14220): #3      _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter (14220): #4      _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter (14220): #5      _FutureListener.handleValue (dart:async/future_impl.dart:140:18)
E/flutter (14220): #6      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:682:45)
E/flutter (14220): #7      Future._propagateToListeners (dart:async/future_impl.dart:711:32)
E/flutter (14220): #8      Future._completeWithValue (dart:async/future_impl.dart:526:5)
E/flutter (14220): #9      _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:33:15)
E/flutter (14220): #10     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:291:13)
E/flutter (14220): #11     Query.getDocuments (package:cloud_firestore/src/query.dart)
E/flutter (14220): <asynchronous suspension>
E/flutter (14220): #12     _MyAppState._onChanged (package:fire/main.dart:102:12)
E/flutter (14220): #13     _MyAppState.build.<anonymous closure> (package:fire/main.dart:559:33)
E/flutter (14220): #14     EditableTextState._formatAndSetValue (package:flutter/src/widgets/editable_text.dart:1607:14)
E/flutter (14220): #15     EditableTextState.updateEditingValue (package:flutter/src/widgets/editable_text.dart:1208:5)
E/flutter (14220): #16     TextInput._handleTextInputInvocation (package:flutter/src/services/text_input.dart:962:36)
E/flutter (14220): #17     MethodChannel._handleAsMethodCall (package:flutter/src/services/platform_channel.dart:402:55)
E/flutter (14220): #18     MethodChannel.setMethodCallHandler.<anonymous closure> (package:flutter/src/services/platform_channel.dart:370:54)
E/flutter (14220): #19     _DefaultBinaryMessenger.handlePlatformMessage (package:flutter/src/services/binding.dart:200:33)
E/flutter (14220): #20     _invoke3.<anonymous closure> (dart:ui/hooks.dart:303:15)
E/flutter (14220): #21     _rootRun (dart:async/zone.dart:1126:13)
E/flutter (14220): #22     _CustomZone.run (dart:async/zone.dart:1023:19)
E/flutter (14220): #23     _CustomZone.runGuarded (dart:async/zone.dart:925:7)
E/flutter (14220): #24     _invoke3 (dart:ui/hooks.dart:302:10)
E/flutter (14220): #25     _dispatchPlatformMessage (dart:ui/hooks.dart:162:5)
E/flutter (14220): 
I/flutter (14220): false
I/chatty  (14220): uid=10288(m20zero.fire) Thread-3 identical 2 lines
I/flutter (14220): false

Answer 1

我会从使用开始

int.tryParse(documentData['price_reduction']);

甚至可能

int.tryParse(documentData['price_reduction']) ?? 0;

而不是

int.parse(documentData['price_reduction']);

也许这会对问题有所了解，您可以从那里开始。