Traversing a Data Structure in Ruby

Data structures have always confused me. Either I get lost when I'm trying to access the nested elements or I just get frustrated take the easy way out to solve a problem.

Let's say I have this hash of hashes:

Code:

---

config = {
      "somehost" => {
            "user" => "bivouac",
            "host" => "www.somehost.com",
            "r_log" => "/home/bivouac/logs"
      },
      "another_host" => {
            "user" => "someone_else",
            "host" => "www.another_host.com",
            "r_log" => "/var/tmp/logs"
      }
    }

---

This is how I'm accessing the elements of the data structure via the command line:

Code:

---

machine = ARGV[0]
    user = config[machine]["user"]
    host = config[machine]["host"]
    r_log = config[machine]["r_log"]
    puts [user, host, r_log].join("\t")

---

Seems too remedial. I already have the variable names (user, host, r_log) so it just seems overkill that I'm using them twice as var names and as hash keys. Anyway...

This is the output:

Code:

---

$ ruby hash.rb somehost
  bivouac www.somehost.com                /home/bivouac/logs

---

I was looking through the Ruby docs and the Pickaxe and I know that the 'hash' object has a 'each_key' method that you can use to access the keys of a hash, but what if those keys access another hash.

Two questions really, what's a more elegant solution and anyone have a good tutorial on data structures could be in any language like PHP, Python or Perl. Just looking for better grounding when I run into these problems.

Well you can check if a value is a hash by using the kind_of? and is_a? methods. The difference is that kind_of? returns true for children of the wanted class too. Example:

Code:

---

config.each do |key, value|
  if value.kind_of?(Hash) then
        # is a hash
  end
end

---

Also, Hash#each allows you to use a key and value :)