firebase 中基于角色的身份验证

Question

我尝试使用以下代码将管理员用户导航到一个特殊页面，但它给出了 NoSuchMethodError 这是代码

 class Home extends StatelessWidget {

  @override
Widget build(BuildContext context) {
final user = Provider.of<User>(context);
return StreamBuilder<DocumentSnapshot>(
  stream: Firestore.instance.collection('users').document(user.uid).snapshots(),
  builder: (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot){
    if(snapshot.hasError){
      return Text('Error: ${snapshot.error}');
    }
    switch(snapshot.connectionState){
      case ConnectionState.waiting: return Loading();
      default:
        return checkRole(snapshot.data);
    }
  
  },
);
 }
Widget checkRole(DocumentSnapshot snapshot){
if(snapshot.data['category']=='admin'){
  return AproveNotice();
}else{
  return HomePage();
}
}
}

这是我的错误

The method '[]' was called on null. Receiver: null Tried calling: []("category")

Answer 1

改变这个：

case ConnectionState.waiting: return Loading();
      default:
        return checkRole(snapshot.data);
    }

对此：

case ConnectionState.waiting: return Loading();
case ConnectionState.done: return checkRole(snapshot.data);
    }

Answer 2

您的 snapshot.data 对象在 null 此处：

if(snapshot.data['category']=='admin'){

这是因为如果对象不存在，快照数据将为空。 Google 建议首先检查它 exists：

https://firebase.google.com/docs/reference/android/com/google/firebase/firestore/DocumentSnapshot

If the DocumentSnapshot points to a non-existing document, getData() and its corresponding methods will return null. You can always explicitly check for a document's existence by calling exists().

firebase 中基于角色的身份验证

role based authentication in firebase

firebase

flutter

dart

google-cloud-firestore

role-base-authorization