From: Rein Henrichs <reinh@...>
Date: 2010-06-18T12:25:29+09:00
Subject: Re: method interface - hash argument vs. named parameters

On 2010-06-17 07:24:47 -0700, Intransition said:

> I've never run into this issue before, but I'm working on a method
> interface that is quite 'dense', and I need to be able to
> differentiate between a hash passed to a method and named parameters.
> i.e. All of these are valid:
> 
>   foo(hash, :opt=>val)
>   foo(hash)
>   foo(:opt=>val)
> 
> However, there seems to be no way to distinguish that last the two
> forms.
> 
> Is there any way? Or am I stuck?

If both the second and third option are valid then there is no way to 
distinguish between the two hashes. If you could narrow it down to one 
of them, you would be ok. If the hash is optional but the options 
aren't, you can use:

def foo(hash_or_options, options=nil)
  hash = options ? hash_or_options : nil
  options = hash_or_options unless options
  ...
end

Alternatively, you can pass the original argument as part of the options hash

foo(:hash => hash, ...)

I assume you're using a more meaningful variable name than 'hash' in 
the real code, so this may suffice. I would not recommend mixing the 
two styles in the same method though (allowing a hash argument OR a 
:hash option).

-- 
Rein Henrichs
http://puppetlabs.com
http://reinh.com