From: Heesob Park <phasis@...>
Date: 2008-05-03T10:08:19+09:00
Subject: Re: How to access to an Array element without doing "find" each time

Hi,

I単aki Baz Castillo wrote:
> Hi, I've an Array containing complex objects of Header class:
> 
> -------------------------------------
> class Header
>   #attributes:
>   # - @name
>   # - @original_value
>   # - @parsed_value
>   # ...
> end
> 
> class Message
>   #attributes:
>   # - @first_line
>   # - @headers =
>   #      [header_1, header_2, header_3...]
>   # - @body
> end
> -------------------------------------
> 
> Just some headers are parsed, and for a header "From", @name attribute 
> can be:
>   "From", "from", "FROM", "F", "f" ... =>   /^(from|f)$/i
> 
> 
> Now I need to access a specifi header ("From" for example) several times 
> and I
> want to avoid doing a "Header.find { |h| h.name =~  /^(from|f)$/i }" for 
> each
> access,so:
> 
> class Message
>   def header(name)
>     Header.find { |h| h.name =~  /^(from|f)$/i }
>   end
> end
> 
> 
> But doing message.header("From") for each access will be not very 
> efficient
> and I try to avoid it. Is there any other way?
> 
> I could doing an assigment just the first time:
> 
>   message.hdr_from = message.header("From")
>   ...do_somethig_with_hdr_from... :
>   message.hdr_from.parsed_value.uri
>   message.hdr_from.parsed_value.uri.name
>   message.hdr_from.parsed_value.display_name
>   ...
> 
> So "hdr_from" is like a pointer to header("From"), but it's not valid 
> for me
> since I need the possibility of doing a re-assignement:
> 
>   header("From") = header("To")
> 
> So if after doing that I use "message.hdr_from" I will access to the 
> previous
> value of "From" header instead of the new one.
> 
> 
> In fact, what I'm looking for is a persister pointer, concept that I 
> already
> know doesn't exist in Ruby :(
>
How about use class variable something like this:

class Message
  def initialize

    @@header = {}
  end
  def header(name)
    return @@header[name] ||= @headers.find { |h| h.name =~ 
/^(from|f)$/i }
  end
end


> Thanks for any suggestion.

Regards,
Park Heesob
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