[Gambas-user] gambas | Draft: DBus, add ConnectionExists boolean property (!238)

[bb]

On Thu, 2021-07-08 at 17:51 +0000, Bruce Steers (@bsteers4) wrote:
> Bruce Steers created a merge request: !238
> 
> Project:Branches: bsteers4/gambas:dbus-connectionexists to
> gambas/gambas:master
> Author: Bruce Steers
> Assignees:
> Reviewers:
> [GB.DBUS]
> 
> NEW: ConnectionExists boolean property sets true if connection fails
> due to already existing connection.
> It's a solution. Or maybe just a workaround? With this if Register()
> fails and ConnectionExists = False i know i have a different error.
> 
> I understand if you think it's not the best idea and you have a
> better idea :)
> 

Bruce,

It's not the connection that is failing. It is the attempted
registration.

>From memory, checking whether a (any) dbus server already exists can be
done by simply trying to connect to it. BUT! as Benoit said, that is
not a "atomic" process.
The way he described is the best way to do such a "set and test" check.

	try(set registration)
	except (set error)

	on_error(do something)
	else (do something else, like attempt to "become" the server*)

So it's actually failing successfully (!)

b

* a BAD idea imo. Servers should serve, clients should be simple and
stupid.
! You also have the problem when using an asynchronous check in that
the server may well exit between the check and the subsequent attempt
to use that server.