Markus,
Thanks for the extended explanation. This is something that should be
stuck up on the Type dev wiki.
I'll try to get around to it, but no promises :-/.
Thanks,
Trevor
On Fri, Mar 4, 2011 at 7:07 PM, Markus Roberts <mar...@puppetlabs.com> wrote:
>
>
>>
>> The title_pattern method is used in resource.rb in the parse_title
>> method. It will expect that you return an (not really intuitive) array
>> of the form
>>
>> [ [ regex1, ARRAY ], [ regex2, ARRAY ] ]
>>
>> with ARRAY = [ [:namevar1, proc_that_is_called_with_namevar1], ...
>> ,[:namevarN, proc ] ]
>>
>> In you example your title_pattern method could return
>> [ [ /^(.*):(.*)$/, [ [ :target, lambda{|x| x} ], [:username, lambda{|x|
>> x}] ] ] ]
>
> At one point this had been simpler but apparently that got refactored away;
> in the older code, if you didn't want the name munged the lambda {|x| x}
> (a.k.a. identity) could be omitted.
>
> The idea here (to render the situation a little more intelligible) is that
> you can specify an ordered list of title patterns, and the first one that
> matches is used to set the corresponding namevar-components. To accomplish
> this, each pattern is associated with an array of property names (as
> symbols) and a munging function (the lambda) which can be used to extract /
> reformat the data. There should be the same number of these as there are
> groups in the regular expression, and they will be passed the matching part
> of the title.
>
> If no pattern matches no properties are set and you have to specify them
> yourself. I believe this basically giver you what you want:
>
>> What I'd like is this:
>>
>> foo { "meaningless_name":
>> target => "/some/path",
>> username => "username"
>> }
>>
>
> with no extra fuss. Because there is only one pattern, so long as
> "meaningless_name" doesn't contain a colon, it won't set any of the
> components of the namevar, and you'll get the uniqueness restrictions you
> want.
>
> You don't have to do:
>
>>
>> Then, in foo.rb, I'd like to be able to say:
>>
>> :namevar = "#{target}:#{username}
>
> because that's in effect a subset of what the composite namevar system is
> doing.
>
> I'd actually advise tightening the regular expression somewhat (as I'd
> originally suggested) to at least make sure the user name was well formed
> (and specifically, did not contain a colon), say something like:
>
> [ [ /^(.+):([a-zA-Z_0-9]+)$/, [ [ :target, lambda{|x| x} ], [:username,
> lambda{|x| x}] ] ] ]
>
> and perhaps even further, to specify valid paths or...?. Since you aren't
> planning on using the decomposition mechanism in most cases, it would make
> sense to have it as tight as reasonably possible so as to prevent it
> "accidentally" doing you any favours, while still leaving it correct* for
> the cases where you do decide to use it.
>
> Conversely, I suppose you could have title_patterns just return:
>
> []
>
> meaning "there are no supported ways to parse the title into namevar
> components" which would require that the target and username always be
> specified and collectively unique within the type, well as the usual
> requirement that the title be unique withing the type.
>
> -- M
> * That is, you'd want to make sure that would still accept all valid user
> names.
> -----------------------------------------------------------
> When in trouble or in doubt, run in circles,
> scream and shout. -- 1920's parody of the
> maritime general prudential rule
> ------------------------------------------------------------
>
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--
Trevor Vaughan
Vice President, Onyx Point, Inc
(410) 541-6699
tvaug...@onyxpoint.com
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