Helper function for constructing AsyncInitable object.
This is similar to newv but also initializes the object asynchronously.
When the initialization is finished, callback will be called. You can then call
new_async.end to get the new object and check for any errors.
| object_type |
a Type supporting AsyncInitable. |
| parameters |
the parameters to use to construct the object |
| io_priority |
the I/O priority of the operation |
| cancellable |
optional Cancellable object, null to ignore. |
| callback |
a AsyncReadyCallback to call when the initialization is finished |
| n_parameters |
the number of parameters in |
| user_data |
the data to pass to callback function |