Flutter Question posted in
The official Flutter documentation can be found here.

How do I decode received data from supabase in Dart/Flutter?

In Dart/Flutter, using the supabase package, I’m trying to decode the data I receive for example from the following code:

final data = await supabase
  .from('countries')
  .select('''
    name,
    cities (
      name
    )
  ''');

How do I do that? Can anyone provide me with an example how I get the resulting Dart objects out of data? How would I e.g. print the table that I get as result?

Code taken from the documentation: https://supabase.com/docs/reference/dart/select

I tried to decode it as if I would decode json but it did not work.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    I solved it as follows (see notes below):

       PostgrestTransformBuilder<List<Map<String, dynamic>>> get _future =>
         Supabase.instance.client
             .from('saved')
             .select()
             .eq('profile_id', supabase.auth.currentUser!.id)
             .order('importance', ascending: false)
             .limit(2);
   
     void fetchData() async {
       try {
         final data = supabase
             .from('saved')
             .select()
             .eq('profile_id', supabase.auth.currentUser!.id)
             .order('importance', ascending: false)
             .limit(2);
         print(data);
         print(jsonDecode(data.toString()));
       } catch (e) {
         print('Fetch error: $e');
       }
     }
   
     @override
     Widget build(BuildContext context) {
       return Scaffold(
         appBar: AppBar(
           title: const Text('Test'),
           actions: [
             TextButton(
                 onPressed: () => setState(() {}),
                 child: const Text('Refresh')),
             TextButton(
                 onPressed: () => fetchData(),
                 child: const Text('Fetch data')),
           ],
         ),
         body: FutureBuilder<List<Map<String, dynamic>>>(
           future: _future,
           builder: (context, snapshot) {
             if (!snapshot.hasData) {
               return const Center(child: CircularProgressIndicator());
             }
             final savedItems = snapshot.data!;
             return ListView.builder(
               itemCount: savedItems.length,
               itemBuilder: ((context, index) {
                 final item = savedItems[index];
                 return ListTile(
                   title: Text(item['pos']),
                 );
               }),
             );
           },
         ),
       );
     }

    Please note:

    • The FutureBuilder builds the widget as intended. This solves my initial problem.
    • Hitting the 'Fetch' button just gets the data, which unfortunately, I still don't know how to decode. As output I get: "Instance of 'PostgrestTransformBuilder<List<Map<String, dynamic>>>'n Fetch error: FormatException: SyntaxError: Unexpected token 'I', "Instance o"... is not valid JSON"

  2. 0

    Here is little code that explain how to use supabase data

    class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Countries',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final _future = Supabase.instance.client
      .from('countries')
      .select();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder<List<Map<String, dynamic>>>(
        future: _future,
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return const Center(child: CircularProgressIndicator());
          }
          final countries = snapshot.data!;
          return ListView.builder(
            itemCount: countries.length,
            itemBuilder: ((context, index) {
              final country = countries[index];
              return ListTile(
                title: Text(country['name']),
              );
            }),
          );
        },
      ),
    );
  }
}

    See Use Supabase with Flutter for details.

    For fetching data without future builder.
    Method 2.

    class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Countries',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
List countries = [];


@override
void initState(){
getCountryData();
super.initState();
}


void  getCountryData()async{
List data = await Supabase.instance.client
      .from('countries')
      .select()
setState((){
countries.addAll(data);
});


}


  final _future = Supabase.instance.client
      .from('countries')
      .select();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body:  countries.isNotEmpty ?ListView.builder(
            itemCount: countries.length,
            itemBuilder: ((context, index) {
              final country = countries[index];
              return ListTile(
                title: Text(country['name']),
              );
):const SizedBox.shrink()
}       
}
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search