Mutliple arguments when Ack

[Oskang09]

Trying to get work with featherjs and unable to work with the direct connection given at documentation.

Worked well after make this fix.
( L150, lib/src/socket.dart )

// But would break other data type
List sendData = data === null ? [event] : [event, ...data];

Example code:

_socket.emitWithAck('get', [ 'product', 78 ],
            ack: (error, data) {
                print(error);
            });

_socket.emitWIthAck('find', [ 'product' ], 
            ack: (error, data) {
                print(error);
            });

And also for arguments when success feathers only return error & data, when error only receive error and dart would throw error.

Error Message:

[ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: Closure call with mismatched arguments: function 'call'

[jumperchen]

FYI: Spread operator only works on Dart 2.3, but our internal project still works with Dart 2.1.

[Oskang09]

I think this work too for concat values for lower than dart 2.3

[].add(event)..addAll(data)

EDIT :

Fixed all issues that i have meet. Thanks for your helping too.

For emiting part:

      List sendData = [event];
      if (data is Iterable) {
          sendData.addAll(data);
      } else if (data != null) {
          sendData.add(data);
      }

For ack part:

           ack: (Map error, [ Map data ]) {
                print(error);
                print(data);
            }