flutter firestore collection snapshots queries tutorial

import ‘package:flutter/material.dart’;

import ‘package:cloud_firestore/cloud_firestore.dart’;
void main() => runApp(new MediaQuery(

    data: new MediaQueryData(), child: new MaterialApp(home: new MyApp())));
class MyApp extends StatelessWidget {

  final databaseReference = Firestore.instance;
  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(

        title: Text(‘FireStore Demo’),

      ),

      body: Center(

          child: Column(

        crossAxisAlignment: CrossAxisAlignment.stretch,

        children: [

          RaisedButton(

            child: Text(‘Create Record’),

            onPressed: () {

              createRecord();

            },

          ),

          RaisedButton(

            child: Text(‘View Record’),

            onPressed: () {

              getData();

            },

          ),

          RaisedButton(

            child: Text(‘Update Record’),

            onPressed: () {

              updateData();

            },

          ),

          RaisedButton(

            child: Text(‘Delete Record’),

            onPressed: () {

              deleteData();

            },

          ),

        ],

      )), //center

    );

  }
  void createRecord() async {

    await databaseReference.collection(“books”)

        .document(“1”)

        .setData({

          ‘title’: ‘Mastering Flutter’,

          ‘description’: ‘Programming Guide for Dart’

        });
    DocumentReference ref = await databaseReference.collection(“books”)

        .add({

          ‘title’: ‘Flutter in Action’,

          ‘description’: ‘Complete Programming Guide to learn Flutter’

        });

    print(ref.documentID);

  }
  void getData() {

    databaseReference

        .collection(“books”)

        .getDocuments()

        .then((QuerySnapshot snapshot) {

      snapshot.documents.forEach((f) => print(‘${f.data}}’));

    });

  }
  void updateData() {

    try {

      databaseReference

          .collection(‘books’)

          .document(‘1’)

          .updateData({‘description’: ‘Head First Flutter’});

    } catch (e) {

      print(e.toString());

    }

  }
  void deleteData() {

    try {

      databaseReference

          .collection(‘books’)

          .document(‘1’)

          .delete();

    } catch (e) {

      print(e.toString());

    }

  }

}