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How can I make sure a method waits for a http response instead of returning null in Dart?




I am trying to write a little command line library in Dart to work with the Facebook API. I have a class 'fbuser' which gets the auth-token and user-id as properties and has a method 'groupIds' which should return a List with all IDs of groups from the user.

When I call the method it returns null altough the two possbile returns are called after the http response. What did I do wrong?

Here is my code:

import 'dart:convert'; //used to convert json 
import 'package:http/http.dart' as http; //for the http requests

final fbBaseUri = "https://graph.facebook.com/v2.1";
final fbAppID = "XXX";
final fbAppSecret = "XXY";

class fbuser {
  int fbid;
  String accessToken;

  fbuser(this.fbid, this.accessToken); //constructor for the object

  groupIds(){ //method to get a list of group IDs
    var url = "$fbBaseUri/me/groups?access_token=$accessToken"; //URL for the API request
    http.get(url).then((response) {
      //once the response is here either process it or return an error
      print ('response received');
      if (response.statusCode == 200) {
        var json = JSON.decode(response.body);
        List groups=[];
        for (int i = 0; i<json['data'].length; i++) {
        print(groups.length.toString()+ " Gruppen gefunden");
        return groups; //return the list of IDs
      } else {
        print("Response status: ${response.statusCode}");
        return (['error']); //return a list with an error element

void main() { 
  var usr = new fbuser(123, 'XYY'); //construct user
  print(usr.groupIds()); //call method to get the IDs

At the moment the output is:

Observatory listening on
response received
174 Gruppen gefunden

The method runs the http request but it returns null immediately.

(I started programming this summer. Thanks for your help.)

like image 243
Luca Avatar asked Mar 19 '23 10:03


1 Answers

return http.get(url) // add return
void main() {
  var usr = new fbuser(123, 'XYY'); //construct user
  usr.groupIds().then((x) => print(x)); //call method to get the IDs
  // or
  usr.groupIds().then(print); //call method to get the IDs
like image 58
Günter Zöchbauer Avatar answered Mar 21 '23 07:03

Günter Zöchbauer