[ruby-core:19958] Re: Proposal: Method#get_args

Just to be clear on the use-case:
The idea is that having better introspection into Ruby methods could help
map inbound parameters (for, say, XML-RPC, REST-based params, or some other
RPC protocol) to the Ruby class. For this purpose, being able to define only
literal defaults is just fine, as inbound RPC or REST parameters are usually
limited to literals as well.

In the case of REST, inbound params are always Strings. I say we start by
exposing just the simple literal set we've already discussed, and add
support for additional literal types (Arrays of literals, for instance) if
there is strong demand.

-- Yehuda

On Sat, Nov 15, 2008 at 3:17 PM, Yehuda Katz <[e-mail]> wrote:

> In our case, we're dealing with inbound web params, so the defaults are
> always strings.
>
> Sent from my iPhone
>
> On Nov 15, 2008, at 2:34 PM, "Roger Pack" <[e-mail]> wrote:
>
>  We need the defaults to handle out-of-order defaults:
>>> def action(bar=1, baz=2); end
>>> Where we get {baz => 5} inbound.
>>>
>>
>> AFAIK this isn't possible in Ruby currently (though might work fine
>> with "simple" values like you said).
>>
>> Some notes:
>>
>> Note that order matters:
>> def action(bar=1, bar2 = bar1); end # valid but note that it needs
>> bar1 to work, and needs it first
>>
>> def action(bar2 = bar1, bar1=0); end # invalid
>>
>> And then the "edge cases" where definitions include assignment are hard:
>>
>> def action(bar=1, baz=(hidden_variable=2), foo=2*baz); end
>>
>> which, if you are given bar and foo, you can't recreate easily that
>> hidden_variable == 2
>>
>> What you want might be something along the lines of
>> object.__send_with_named_variables__ :action, :baz => 5
>> though I'm not sure how it would work.
>>
>> With access to the AST you can write "wrappers" to methods [which
>> still wouldn't help with the hidden_variable fella, except raising if
>> you find it, but work besides that] [1].
>>
>> Was there a plan for named parameters in 2.0?  That might be the way to
>> go.
>>
>>
>> -=R
>>
>> [1]
>> http://code.google.com/p/ruby-roger-useful-functions/wiki/NamedParameters
>>
>>
>


-- 
Yehuda Katz
Developer | Engine Yard
(ph) 718.877.1325