From: Joel VanderWerf <vjoel@...>
Date: 2006-03-27T04:29:28+09:00
Subject: Re: Verifying keyword arguments

Eli Bendersky wrote:
> Joel VanderWerf wrote:
>> Ross Bamford wrote:
>> ..
>>> Not sure about libraries (though I'm sure they are out there, check RAA
>>> and Rubyforge) but here's a little trick I've used before:
>>>
>>> args = { :one => 'two', :three => 'four' }
>>> # => {:three=>"four", :one=>"two"}
>>>
>>> h = Hash.new { |h,k| raise ArgumentError, "#{k}" }.merge(args)
>>> # => {:three=>"four", :one=>"two"}
>>>
>>> h[:one]
>>> # => "two"
>>>
>>> h[:three]
>>> # => "four"
>>>
>>> h[:two]
>>> ArgumentError: two
>>>         from (irb):5
>>>         from (irb):11
>>>
>>> This way, you never actually check the arguments explicitly, but you'll
>>> be told if your method uses one that wasn't passed. Obviously for
>>> optional arguments you go to the original hash.
>>>
>> What about using rescue for optional arguments? It might be slower though.
>>
> 
> What do you mean ? Can you provide an example ?
> 

args = { :one => 'two', :three => 'four' }
# => {:three=>"four", :one=>"two"}

h = Hash.new { |h,k| raise ArgumentError, "#{k}" }.merge(args)
# => {:three=>"four", :one=>"two"}

h[:one]
# => "two"

h[:three]
# => "four"

v = h[:two] rescue "this string is the default for 'two'"
p v
# => "this string is the default for 'two'"

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407