From: Roger Pack <rogerpack2005@...>
Date: 2008-11-16T07:34:10+09:00
Subject: [ruby-core:19956] Re: Proposal: Method#get_args

> 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