Fetch specific data from Firebase Realtime Database in Flutter

Question

I want to check if the specific number exists in database so it will fetch the password corresponding to the number or else it will return number does not exist in database in Flutter.

var dbRef = FirebaseDatabase.instance.reference().child("NewUsers");
dbRef.equalTo(numberController.text).once().then((DataSnapshot snapshot){
  if(snapshot.value.isNotEmpty){
    var dbRef = FirebaseDatabase.instance.reference();
    dbRef.child(numberController.text).once().then((DataSnapshot snapshot){
      snapshot.value.forEach((key,values) {
        print(values["Password"]);
      });
    });
  }
  else{
    print("pleasesignup first");
  }
});

After this I'm getting the error Unhandled Exception: NoSuchMethodError: The getter 'isNotEmpty' was called on null

The number above the first unique key which starts with 9971*******. I've to fetch one value at a time. — dartKnightRises
– dartKnightRises, Commented Apr 1, 2020 at 10:01

Peter Haddad · Accepted Answer · 2020-04-01 13:36:22Z

4

Try the following:

var dbRef = FirebaseDatabase.instance.reference().child("newUsers");
dbRef.orderByKey().equalTo(numberController.text).once().then((DataSnapshot snapshot){
     if(snapshot.value.isNotEmpty){
         var ref = FirebaseDatabase.instance.reference("newUsers");
           ref.child(numberController.text).once().then((DataSnapshot snapshot){
                print(snapshot.value); 
                snapshot.value.forEach((key,values) {
                   print(values["Password"]);
              });
          });
       }
   });

First add a reference to the newUsers and using the query orderByKey().equalTo(numberController.text) and then by doing snapshot.value.isNotEmpty it will check if key exists in the database, if it does retrieve the password.

edited Apr 1, 2020 at 13:36

answered Apr 1, 2020 at 9:05

Peter Haddad

81.2k26 gold badges148 silver badges149 bronze badges

Sign up to request clarification or add additional context in comments.

17 Comments

dartKnightRises Over a year ago

I'm getting this error ** Unhandled Exception: NoSuchMethodError: The getter 'isNotEmpty' was called on null.**

Amin Over a year ago

That error means you called the method on a null value - so check if your snapshot.value is returning null

Peter Haddad Over a year ago

your code is different than what I provided.. what is newUsers? There is no child("NewUsers") node in your database

dartKnightRises Over a year ago

Actually the number whose existence I'm looking for is the child of NewUsers.

Peter Haddad Over a year ago

before if(snapshot.value.isNotEmpty){ check if(snapshot.value !=null)

|

Muhammad Noman · Accepted Answer · 2020-04-01 12:56:33Z

0

Try this:

var dbRef = FirebaseDatabase.instance.reference().child("newUsers");
dbRef.orderByKey().equalTo(numberController.text).once().then((DataSnapshot snapshot){
     if(snapshot && snapshot.value){
         var ref = FirebaseDatabase.instance.reference("newUsers");
         ref.child(numberController.text).once().then((DataSnapshot snapshot){
           print(snapshot.value); 
           snapshot.value.forEach((key,values) {
             print(values["Password"]);
          });
        });
     }
     else{
       print("No Record Found");
     }
 });

answered Apr 1, 2020 at 12:56

Muhammad Noman

1,3761 gold badge15 silver badges29 bronze badges

2 Comments

dartKnightRises Over a year ago

I'm getting error on if condition of snapshot, it says the operand of && operation must be assigned to bool.

dartKnightRises Over a year ago

Even I cannot directly pass the reference in instance.reference(" ").it says 0 positional argument expected and found one so I tried by providing reference in its child, but didn't work.

Collectives™ on Stack Overflow

Fetch specific data from Firebase Realtime Database in Flutter

2 Answers 2

17 Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

17 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related