Cannot build up a string using StringBuffer and a server response - dart

Question

I'm trying to fetch data from this link via Dart. Since I'm making use of dart:io library's HttpClientResponse based instance to listen to the data obtained from the above link, therefore I thought that an instance of StringBuffer would be the best option to capture the received data. It would help me to build the response string in an incremental fashion. But it seems like I'm not making proper use of StringBuffer, because in the end the response string (stored in receivedBuffer) remains empty.
Code:
import 'dart:io';
import 'dart:convert';
void main() async
{
StringBuffer receivedBuffer = new StringBuffer("");
String url = "https://hacker-news.firebaseio.com/v0/topstories.json?print=pretty";
HttpClient client = new HttpClient();
HttpClientRequest request = await client.getUrl(Uri.parse(url));
HttpClientResponse response = await request.close();
print("[info] Fetch successful. Proceeding to transform received data ...");
response.transform(utf8.decoder).listen((contents) => receivedBuffer.write(contents));
print("[info] Done. Contents:\n");
print(receivedBuffer);
}
Output :
[info] Fetch successful. Proceeding to transform received data ...
[info] Done. Contents:
Also, instead of receivedBuffer.write(contents), if I were to write print(contents), then all the
required data is printed as one would expect it to. But while trying to write the contents to recievedBuffer it seems like receivedBuffer wasn't even updated once.
I read this article, and tried to incorporate the answer present over there in my code. To be precise, I made use of Completer instance to take care of my issue, but it didn't help.
What's the issue in the above provided code?

Answer 1

You are not waiting for the stream to complete.
In the listen call, you set up a receiver for stream events, but you don't wait for the events to arrive.
You can either add an onDone parameter to the listen call and do something there, but more likely you will want to just wait for it here, and then I recommend:
await response.transform(utf8.decoder).forEach(receivedBuffer.write);
Using forEach is usually what you want when you are calling listen, but not remembering the returned subscription. Alternatively use an await for:
await for (var content in response.transform(utf8.decoder)) {
receivedBuffer.write(content);
}
(which corresponds to a forEach call in most ways).