From: Florian Gilcher <flo@...>
Date: 2009-12-14T12:12:06+09:00
Subject: Re: What is the :argument syntax about?


On Dec 13, 2009, at 11:26 PM, Omar Campos wrote:

> Hi all,
>
> I've noticed that for some methods in some gems, it's necesarry to  
> pass
> arguments like this:
>
> method( :arg1 => value, :arg2 => value, :arg3,...)
>
> I use the syntax the same way in the examples and it works, but I'd
> like to know what Ruby's doing under there.  What is the :  and the =>
> for anyway?  Thanks for any info.

It is the same as:

   method( {:arg1 => value, :arg2 => value} )

{a => b} is a Hash in Ruby, :something is a Symbol. You can read about
those everywhere, I will not write yet another introduction.
Because the parser can easily see that it is a Hash, you can omit the  
{}.

On the other side, it will look like this:

   def method(options = {})
     arg1 = options[:arg1]
     arg2 = options[:arg2]
   end

It looks a bit like named arguments and has the same benefits: you can
reorder them as you like, you immediately know the meaning from the
argument list and you can omit optional arguments in a nice fashion.

Regards,
Florian