Flutter- dart http library ClientException

Question

I am doing a post request like this in flutter using HTTP dart package but sometimes when the network fails a ClientException is thrown from IOClient class but I don't get anything in catch block and app crashes.

http.post(url, headers: headers, body: body).then((response) {
  //response parsing
}).catchError((error) {
 //ClientException is never catched in this block.
});

Answer 1

As mentioned in package:http/src/io_client.dart:

Any internal HTTP errors should be wrapped as [ClientException]s.

As mentioned in the docs this is a clear case of:

Potential problem: accidentally mixing synchronous and asynchronous errors

To resolve this issue, you need to wrap your code in Future.sync().

Future.sync() makes your code resilient against uncaught exceptions. If your function has a lot of code packed into it, chances are that you could be doing something dangerous without realizing it:

return new Future.sync(() {
  http.post(url, headers: headers, body: body).then((response) {});
});

Future.sync() not only allows you to handle errors you know might occur, but also prevents errors from accidentally leaking out of your function.