如何获取从 Dart Flutter Firebase 检索到的数据的值？

Question

I have a code like this:

  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  FirebaseFirestore FS = FirebaseFirestore.instance;

  CollectionReference TC = FirebaseFirestore.instance.collection("oneSignal");
  var docs = TC.doc("xcG9kfCWnUK7QKbK37qd");
  var response = await docs.get();
  
  var veriable = response.data();
  print(veriable);

I'm getting an output like this:

{id: 5138523951385235825832}

I only want the value from this output, namely 5138523951385235825832 . How can I do that?

Answer 1

Your response is a DocumentSnapshot , so response.data() returns a Map with all the fields. To get a specific field from it you can do:

var veriable = response.data() as Map;
print(veriable["id"]);

Alternatively you can get the field directly from the response with:

print(response.get("id"));

For situations like that I recommend keeping the documentation handy, in this case for DocumentSnapshot .

Answer 2

response.data() returns a Map. A Map is a key-value pair. In Dart value of a Map can be accessed using a key.

void main() { 
   var details = {'Usrname':'tom','Password':'pass@123'}; 
   details['Uid'] = 'U1oo1'; 
   print(details); 
} 

It will produce the following output −

{Usrname: tom, Password: pass@123, Uid: U1oo1}

In your case, you can get the value of id using veriable['id']