From: Bryan JJ Buckley <jj@...>
Date: 2008-05-30T00:55:49+09:00
Subject: Re: How can a code block access an object's variables?

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You can pass arguments to block.call which can then be accessed by the 
block.

  block.call(line)

And then when when calling your method, use

    my_reader.each_line do |myline|
      # myline holds the value of "line"
      puts myline
    end

There's a decent introduction to blocks in the Pickaxe book. 
(http://whytheluckystiff.net/ruby/pickaxe/html/tut_containers.html)

Jacob Rubynovice wrote:
> Dear Rubyists,
>
> I am a novice Ruby developer who is interested in figuring out a way to
> design something like what is demonstrated below.  The reason why
> each_line would not work in this example is because when you pass a
> block of code to the FileReader object, the memory (members of
> FileReader) is not shared with the block of code that is sent to
> FileReader.
>
> Maybe I have the wrong idea for how this would be designed.  I just
> think it would be very convenient to do this sort of thing because I
> could re-use the code to open a file and read lines and only pass it
> code blocks pertainant to what I want to do with those lines of code.
>
> Please note that I do not only want to do this for an open file/read
> line script.  It would also be useful if you were expanding an IP range
> that exceeds what you could store into an array object because you could
> write an each_host method that takes in a block of code that relates to
> what you want to do to each host.
>
> class FileReader
>
>    def initialize(fname, &block)
>      @filename = fname
>    end
>    def each_line(&block)
>      begin
>        source = File.new(@filename, "r")
>      rescue => err
>        exit
>      end
>      begin
>        while(line = source.readline)
>
>          line.strip!
>          if((line == "") || (line =~ /[\t+\s+]/))
>            next
>          end
>          block.call
>        end
>      rescue EOFError
>        source.close
>      rescue => err
>        puts "[!] #{err}"
>        exit
>      end
>    end
>
> end
> my_reader = FileReader.new(ARGV[0])
> my_reader.each_line { puts line
>     # do more parsing stuff here
>  }
>   

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