From: Robert Klemme <shortcutter@...>
Date: 2010-01-02T20:50:06+09:00
Subject: Re: block.call

On 01/02/2010 11:47 AM, Ruby Newbee wrote:
> Hello gurus,
> 
> please see the code below, why passing a block to a function then call
> block.call in the function will get success, but run block.call out of
> a function will get failed?
> 
> 
> irb(main):023:0* def myhi(&block)
> irb(main):024:1>   block.call
> irb(main):025:1> end
> => nil
> 
> irb(main):026:0> myhi { puts "hi welcome" }
> hi welcome
> => nil
> 
> irb(main):027:0> { puts "hi welcome" }.call
> SyntaxError: (irb):27: syntax error, unexpected tSTRING_BEG, expecting
> keyword_do or '{' or '('
> { puts "hi welcome" }.call
>         ^
> (irb):27: syntax error, unexpected '}', expecting $end
> { puts "hi welcome" }.call
>                      ^
>         from /usr/bin/irb:12:in `<main>'

Because, as the error message says, this is not valid Ruby syntax.  You 
can use "lambda" or "proc" instead:

irb(main):001:0> lambda { puts "hi" }.call
hi
=> nil
irb(main):002:0>

But this is really useless, i.e. in that case you should simply do "puts 
'hi'".  The lambda notation really only makes sense if you want to store 
the block away for later usage.  Note, that there is also this syntax 
(in case you want to structure your code):

begin
   puts 'hi'
end


Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/