From: Brian Candler <b.candler@...>
Date: 2009-11-23T06:56:57+09:00
Subject: Re: confuse about initialize hash

Zhenning Guan wrote:
> Brian Candler wrote:
> 
>> It is a special case: when the last argument to a method call is a hash, 
>> then you can omit the outer braces.
> 
> 
> the hash options I saw in atom_feed , but it doesn't the last argument.

Is it the &block that bothers you?

That's another special bit of syntax. It allows you to capture the 
passed block into a variable. For example,

  def foo
    yield 123
  end

is pretty much the same as

  def foo(&blk)
    blk.call(123)
  end

But in the second case, since the block itself is bound to a variable, 
you can in turn pass the block around to other methods.

You might call foo like this:

  foo { |x| puts "The value is #{x}" }
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   This is the 'block' I'm talking about

So the block is a hidden argument which comes after all the other 
arguments, and unless you ask for it with &, it's entirely hidden. So 
the last *real* argument may be a hash without its outer braces. I hope 
that's a bit clearer :-)
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