From: Robert Klemme <shortcutter@...>
Date: 2011-01-26T22:59:22+09:00
Subject: Re: IO from text file

On Wed, Jan 26, 2011 at 1:04 PM, Michael Litton <macentricruby@me.com> wrote:
> Thanks for the excellent advice as I now have the correct information
> when I run the code. I am slowly working on a program where I ask a user
> for a selection, compare the selection to a file, then assign that
> selection(two pieces of information) to a variable to be used later.
>
> In your opinion should this data file be YAML, csv, or something else? I
> am only looking at less than 100 records.

The format of that file does not really matter - all these are proper
options.  I suggest you base your decision on what's most convenient
for the producer of the file (user manual typing, spreadsheet or
database export, ...).

If you want to ask the user multiple times and given the size of the
file you should consider loading the file into a data structure which
gives you efficient access (e.g. a Hash with proper key values) so you
don't have to read the file repeatedly.  This will be faster than
having to go to the file over and over again.  If you use YAML you can
directly load the file into the Hash:

14:54:54 Temp$ irb19 -r yaml
Ruby version 1.9.2
irb(main):001:0> h={};10.times {|i| h["key #{i}"]="value #{i}"}
=> 10
irb(main):002:0> h
=> {"key 0"=>"value 0", "key 1"=>"value 1", "key 2"=>"value 2", "key
3"=>"value 3", "key 4"=>"value 4", "key 5"=>"value 5", "key 6"=>"value
6", "key 7"=>"value 7", "key 8"=>"value 8", "key 9"=>"value 9"}
irb(main):003:0> s = h.to_yaml
=> "--- \nkey 0: value 0\nkey 1: value 1\nkey 2: value 2\nkey 3: value
3\nkey 4: value 4\nkey 5: value 5\nkey 6: value 6\nkey 7: value 7\nkey
8: value 8\nkey 9: value 9\n"
irb(main):004:0> puts s
---
key 0: value 0
key 1: value 1
key 2: value 2
key 3: value 3
key 4: value 4
key 5: value 5
key 6: value 6
key 7: value 7
key 8: value 8
key 9: value 9
=> nil
irb(main):005:0> h2 = YAML.load(s)
=> {"key 0"=>"value 0", "key 1"=>"value 1", "key 2"=>"value 2", "key
3"=>"value 3", "key 4"=>"value 4", "key 5"=>"value 5", "key 6"=>"value
6", "key 7"=>"value 7", "key 8"=>"value 8", "key 9"=>"value 9"}
irb(main):006:0> h == h2
=> true
irb(main):007:0>

For reading YAML from a file you can use a 1liner:

hash = File.open("data") {|io| YAML.load(io)}

Kind regards

robert

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