[Libguestfs] example script for GObject

[Matthew Booth]

On 01/26/2012 11:54 AM, Hilko Bengen wrote:
> * Richard W.M. Jones:
>
>>    var optargs = new Guestfs.AddDriveOpts ({readonly: true});
>>    g.add_drive_opts (filename, optargs);
>>
>> This awkward style is required because GObject Introspection doesn't
>> support optional arguments.
>
> This is really, really ugly. Couldn't one use some sort of list instead?
>
> Something that could be translated to Javascript as
>
>      g.add_drive_opts (filename, [ Guestfs.AddDriveOpts.FORMAT, "raw" ] )
>
> or even
>
>      g.add_drive_opts (filename, Guestfs.AddDriveOpts.FORMAT, "raw" )
>
> would be much nicer.

We went round the houses on this one. The main advantage of the optargs 
object is that it's typesafe. It's also quite a lot more concise than 
the [ GUESTFS_VERYVERYVERYLONG_OPTIONNAME, "value" ] format as soon as 
you've got 2 optional arguments.

Note that you can shorten the syntax further by declaring the optargs 
object inline. Compare:

g.add_drive_opts (filename, [Guestfs.AddDriveOpts.FORMAT, "raw"])

with:

g.add_drive_opts (filename, new Guestfs.AddDriveOpts({format: "raw}))

There's barely any difference, and for 2 options the latter would be 
much shorter.

Yes, it would be nicer to have proper optional arguments, but GObject 
Introspection is constrained somewhat by being a meta-binding.

Matt
-- 
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

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