Open Stack

On 06/11/2014 8:32 AM, "Clint Byrum" <clint at fewbar.com> wrote:
>
> Excerpts from Lee, Alexis's message of 2014-11-05 15:46:43 +0100:
> > I'm considering adding a function which takes a list and returns the
first
> > non-null, non-empty value in that list.
> >
> > So you could do EG:
> >
> >     some_thing:
> >         config:
> >             ControlVIP:
> >                 first_nonnull:
> >                 - {get_param: ControlVIP}
> >                 - {get_attr: [ControlVirtualIP, fixed_ips, 0,
ip_address]}]}
> >
> > I'm open to other names, EG "some", "or", "fallback_list" etc.
> >
> > Steve Hardy suggested building this into get_attr or Fn::Select. My
feeling
> > is that those each do one job well right now, I'm happy to take a steer
> > though.
> >
> > What do you think please?
> >
>
> Yes this is super useful for writing responsive, reusable templates.
>
> I'd like to suggest that this be called 'coalesce' as that is what SQL
> calls it.

Although I have no clue why they called it that (colalesce mean join/merge
not get first non-null). I'd rather it be called what it does
"first_nonnull()" seems more obvious to me. We could also try the
conditional as Zane suggested.

-Angus

>
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