From: MonkeeSage <MonkeeSage@...>
Date: 2007-12-07T22:30:02+09:00
Subject: Re: printing on new lines

On Dec 7, 6:18 am, Johnathan Smith <stu...@hotmail.com> wrote:
> hello
>
> iv written a class which prints a a number of hashes of refrences
>
> however it all prints on one line. What i was wondering was it is
> possible to print each reference on a different line.
>
> Any help would be much appreciated
> my code is below
>
> thanks
>
>  $linecount = 0
>
>   database = {}
>
>   opts.each do |opt, arg|
>     case opt
>       when '--style'
>          require arg
>       when '--database'
>
>   File.open(arg) { | handle |
>   last_tag = nil
>
>   handle.each { | line |
>
>   m = line.match(/^(\w+):\s*([\w+,\s]+)$/i)
>
>     if m # if m is a match (i.e., not nil)
>
>       if m[1] == 'Tag' # adds a key to the hash
>
>         last_tag = m[2].chomp
>
>         database[last_tag] = {} # makes a subhash as the value
>
>       else
>
>         database[last_tag][m[1]] = m[2].chomp
>
>       end
>
>     end
>
>     }
>
>   }
>
>     end
>   end
>
>   print "Number of References: ", database.length, "\n" # prints number
> of references
>
>   print "Hash Contents: ", database.inspect, "\n" # prints hash contents
> --
> Posted viahttp://www.ruby-forum.com/.

Hello Jonathan,

For readability and reusability you should extract the database making
code out of the when block and into its own method (and $linecount is
obsolete now), so...

====

def make_database(filename)
  database = {}
  File.open(filename) { | handle |
    last_tag = nil
    handle.each { | line |
      m = line.match(/^(\w+):\s*([\w+,\s]+)$/i)
      if m # if m is a match (i.e., not nil)
        if m[1] == 'Tag' # adds a key to the hash
          last_tag = m[2].chomp
          database[last_tag] = {} # makes a subhash as the value
        else
          database[last_tag][m[1]] = m[2].chomp
        end
      end
    }
  }
  return database
end

database = {}

## where is opts coming from in this code??

opts.each do |opt, arg|
  case opt
    when '--style'
      require arg
    when '--database'
      database = make_database(arg)
  end
end

====

Now after #make_database has been called, you can do whatever you like
with the database hash, for example (assuming your previous
reference.txt), to print out a sorted inventory with metadata:

====

# this makes an array of arrays, and each
# subarray is an array of strings, sorted
# on the hash keys, which are composed of
# each hash entry and its subhash data
refs = database.keys.sort.map { | title |
  subhash = database[title]
  ["Reference: #{title}",
   "Type:      #{subhash['Type']}",
   "Author:    #{subhash['Author']}"]
}

# refs now looks like:
#[["Reference: ref1",
#  "Type:      Book",
#  "Author:    Little, S R"],
# ["Reference: ref2",
#  "Type:      Journal",
#  "Author:    Smith, J"],
# ["Reference: ref3",
#  "Type:      Conference Paper",
#  "Author:    Williams, M"]]

refs.each_with_index { | ref, i |
  puts ref # puts automatically prints each
           # item of an array on a new line

  # print a newline in between refs unless
  # its the last one
  puts if i < refs.length-1
}

====

This outputs:

Reference: ref1
Type:      Book
Author:    Little, S R

Reference: ref2
Type:      Journal
Author:    Smith, J

Reference: ref3
Type:      Conference Paper
Author:    Williams, M

Look at the Hash and Array classes to see exactly what these methods
are doing:

http://www.ruby-doc.org/core/classes/Hash.html
http://www.ruby-doc.org/core/classes/Array.html

Regards,
Jordan