不知道我从哪里得到 NoSuchMethodError: '[]'
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【中文标题】不知道我从哪里得到 NoSuchMethodError: \'[]\'【英文标题】：No idea where I'm getting NoSuchMethodError: '[]'不知道我从哪里得到 NoSuchMethodError: '[]' 【发布时间】：2021-11-07 13:48:42 【问题描述】：我正在使用 python framework-django、graphql、flutter 制作一个演示登录应用程序，如下所示。
这是一个非常简单的测试应用，但我得到“NoSuchMethodError='[]'”，而且我已经在这个问题上花费了几个小时。
我收到的错误消息如下。
The user wants to create an account with dsafds@asdfasd.com and dasdfadsf dart_sdk.js:28087
There was an error!
Uncaught (in promise) Error: NoSuchMethodError: '[]'
Dynamic call of null.
Receiver: null
Arguments: [0]
at Object.throw_ [as throw] (:58141/dart_sdk.js:5348)
at Object.defaultNoSuchMethod (:58141/dart_sdk.js:5793)
at Object.noSuchMethod (:58141/dart_sdk.js:5788)
at callNSM (:58141/dart_sdk.js:5521)
at Object._checkAndCall (:58141/dart_sdk.js:5523)
at Object.callMethod (:58141/dart_sdk.js:5601)
at Object.dsend (:58141/dart_sdk.js:5604)
at main._LoginPageState.new._createAccountPressed (:58141/packages/auth_frontend/main.dart.lib.js:1003)
at _createAccountPressed.next (<anonymous>)
at :58141/dart_sdk.js:39230
at _RootZone.runUnary (:58141/dart_sdk.js:39087)
at _FutureListener.thenAwait.handleValue (:58141/dart_sdk.js:34073)
at handleValueCallback (:58141/dart_sdk.js:34633)
at Function._propagateToListeners (:58141/dart_sdk.js:34671)
at _Future.new.[_completeWithValue] (:58141/dart_sdk.js:34513)
at async._AsyncCallbackEntry.new.callback (:58141/dart_sdk.js:34536)
at Object._microtaskLoop (:58141/dart_sdk.js:39374)
at _startMicrotaskLoop (:58141/dart_sdk.js:39380)
at :58141/dart_sdk.js:34887
Flutter Doctor 结果如下
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.2.3, on Microsoft Windows [Version 10.0.19043.1165], locale en-US)
[√] android toolchain - develop for Android devices (Android SDK version 31.0.0)
[√] Chrome - develop for the web
[√] Android Studio (version 4.1.0)
[√] VS Code (version 1.60.0)
[√] Connected device (2 available)
• No issues found!
我的颤振项目代码如下（我排除了不重要的行）
import 'package:flutter/material.dart';
// ignore: import_of_legacy_library_into_null_safe
import 'package:graphql_flutter/graphql_flutter.dart';
import 'graphql_config.dart';
import 'graphql_query.dart';
void main()
WidgetsFlutterBinding.ensureInitialized();
runApp(
GraphQLProvider(
client: GraphQLConfiguration.initializeClient(),
child: CacheProvider(child: MyApp()),
),
);
class MyApp extends StatelessWidget
// This widget is the root of your application.
const MyApp(Key? key) : super(key: key);
@override
Widget build(BuildContext context)
return MaterialApp(
title: 'My first Django plus Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.red,
),
home: LoginPage(),
);
class LoginPage extends StatefulWidget
const LoginPage(Key? key) : super(key: key);
@override
_LoginPageState createState() => _LoginPageState();
enum FormType login, register
class _LoginPageState extends State<LoginPage>
GraphQLConfiguration graphQLConfiguration = GraphQLConfiguration();
QueryMutation addMutation = QueryMutation();
final TextEditingController _emailFilter = TextEditingController();
final TextEditingController _passwordFilter = TextEditingController();
String _email = "";
String _password = "";
FormType _form = FormType.login;
_LoginPageState()
_emailFilter.addListener(_emailListen);
_passwordFilter.addListener(_passwordListen);
void _emailListen()
if (_emailFilter.text.isEmpty)
_email = "";
else
_email = _emailFilter.text;
void _passwordListen()
if (_passwordFilter.text.isEmpty)
_password = "";
else
_password = _passwordFilter.text;
....
@override
Widget build(BuildContext context)
return Scaffold(
appBar: AppBar(
title: Text("Python & Flutter Login by Hong"),
centerTitle: true,
),
body: Container(
padding: EdgeInsets.all(16.0),
child: Column(
children: <Widget>[
_buildTextFields(),
_buildButtons(),
],
),
),
);
Widget _buildTextFields()
return Container(
child: Column(
children: <Widget>[
Container(
child: TextField(
controller: _emailFilter,
decoration: InputDecoration(labelText: 'Email'),
),
),
Container(
child: TextField(
controller: _passwordFilter,
decoration: InputDecoration(labelText: 'Password'),
obscureText: true,
),
)
],
),
);
Widget _buildButtons()
if (_form == FormType.login)
return Container(
child: Column(
children: <Widget>[
ElevatedButton(
child: Text('Login'),
onPressed: _loginPressed,
),
TextButton(
child: Text('Don have an account? Tap here to register'),
onPressed: _formChange,
),
TextButton(
child: Text('Forgot Password?'),
onPressed: _passwordReset,
),
],
));
else
return Container(
child: Column(
children: <Widget>[
ElevatedButton(
child: Text('Create an Account'),
onPressed: _createAccountPressed,
),
TextButton(
child: Text('Don have an account? Tap here to login'),
onPressed: _formChange,
),
],
));
...
void _createAccountPressed() async
print('The user wants to create an account with $_email and $_password');
GraphQLClient _client = graphQLConfiguration.clientToQuery();
QueryResult result = await _client.mutate(
MutationOptions(
// ignore: deprecated_member_use
document: addMutation.register('$_email', '', '$_password'),
),
);
if (result.data["success"] != null)
print('The user was created successfully!');
else
print('There was an error!');
print(result.data["register"]["errors"]["email"][0]["message"]);
...
import "package:flutter/material.dart";
// ignore: import_of_legacy_library_into_null_safe
import 'package:graphql_flutter/graphql_flutter.dart';
// ignore: import_of_legacy_library_into_null_safe
import 'package:shared_preferences/shared_preferences.dart';
class GraphQLConfiguration
static final HttpLink httpLink = HttpLink(
uri: "http://127.0.0.1:8000/graphql",
);
static final AuthLink authLink = AuthLink(getToken: () async
SharedPreferences pref = await SharedPreferences.getInstance();
return pref.getString("token");
);
static final Link link = authLink.concat(httpLink);
static ValueNotifier<GraphQLClient> initializeClient()
ValueNotifier<GraphQLClient> client = ValueNotifier(
GraphQLClient(
link: link,
cache: OptimisticCache(dataIdFromObject: typenameDataIdFromObject),
),
);
return client;
GraphQLClient clientToQuery()
return GraphQLClient(
link: link,
cache: OptimisticCache(dataIdFromObject: typenameDataIdFromObject),
);
class QueryMutation
String register(String email, String user, String password)
return """
mutation
register(
email: "$email",
username: "$user",
password1: "$password",
password2: "$password",
)
success,
errors,
token,
refreshToken
""";
"""
Generated by 'django-admin startproject' using Django 3.2.7.
...
"""
from pathlib import Path
ALLOWED_HOSTS = []
# Application definition
INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'users',
'graphene_django',
'graphql_jwt.refresh_token.apps.RefreshTokenConfig',
"graphql_auth",
'django_filters',
'corsheaders',
]
AUTH_USER_MODEL = 'users.CustomUser'
MIDDLEWARE = [
'corsheaders.middleware.CorsMiddleware',
'django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware',
]
CORS_ORIGIN_ALLOW_ALL = True
GRAPHENE =
'SCHEMA': 'auth2.schema.schema', # this file doesn't exist yet
'MIDDLEWARE': [
'graphql_jwt.middleware.JSONWebTokenMiddleware',
],
GRAPHQL_JWT =
"JWT_VERIFY_EXPIRATION": True,
# optional
"JWT_LONG_RUNNING_REFRESH_TOKEN": True,
"JWT_ALLOW_ANY_CLASSES": [
"graphql_auth.mutations.Register",
],
AUTHENTICATION_BACKENDS = [
# 'graphql_jwt.backends.JSONWebTokenBackend',
'django.contrib.auth.backends.ModelBackend',
"graphql_auth.backends.GraphQLAuthBackend",
]
EMAIL_BACKEND ='django.core.mail.backends.console.EmailBackend'
ROOT_URLCONF = 'auth2.urls'
TEMPLATES = [
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [],
'APP_DIRS': True,
'OPTIONS':
'context_processors': [
'django.template.context_processors.debug',
'django.template.context_processors.request',
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
],
,
,
]
WSGI_APPLICATION = 'auth2.wsgi.application'
DATABASES =
'default':
...
AUTH_PASSWORD_VALIDATORS = [
...
]
...
我假设异步/等待的事情有问题，但我不太确定。 我一直在尝试多种方法，但似乎它变得更加复杂。
任何建议将不胜感激！
【问题讨论】：
【参考方案1】：我相信你在这里的 main.dart 中打错了，你应该像这样进入你的地图：
if ((result.data["mutation"])["success"] != null)
...
应该是成功而不是成功。
此外，为了访问地图，您应该注意在必要时使用括号：
print((((((result.data["register"])["errors"])["email"])[0])["message"]));
【讨论】：
非常感谢您告诉我。愚蠢的错误。但是在得到固定的TT后它仍然不起作用 注释掉这部分，看看错误是否消失： print(result.data["register"]["errors"]["email"][0]["message"]); 仍然，同样的错误，但我可以看到 [成功] ...我确定新用户已成功注册，但只是 NoSuchMethod 错误不断出现，=> 用户想要创建一个帐户dsasdf@dsafds.com 和 dafsdfads。用户名是 dsasdf 错误：NoSuchMethodError: '[]' 动态调用 null。接收者：null 参数：["success"] at Object.throw_ [as throw] (localhost:52989/dart_sdk.js:5348:11) .... 这样做：(result.data["mutation"])["success"];【参考方案2】：在我添加 Cors 之前遇到了同样的问题，它对我有用
MIDDLEWARE_CLASSES = (
...
'corsheaders.middleware.CorsMiddleware',
'django.middleware.common.CommonMiddleware',
...
)
【讨论】：
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