Question

I’m developing a model which holds configuration settings for server options. The number and type of server options change, and I need some input on the pros/cons of two ways of doing it.
I’m doing this separate from the rails ActiveRecord database. All my database interactions are going to be manually with the file system.

First, having the model dynamically create attributes as needed for each server specified. (as long as this is possible… I’ve never done it before)

Second, creating a single Hash, which has Keys of the server options, and values of the server settings.

I think the second would be easier to implement, but I’m not sure if it is the right way to go? It seems to be cleaner to go with dynamic attributes.

Is there a rule of thumb to go with for this?

Answer 1

Made something for you.

Here is how it would work.

s = Settings.new(SettingsFileManager.new(some_file))

s.ip # returns whats in the file.
s.ip = 10.0.0.1 # overrides the new value.

I haven’t written the way it interacts with the files yet so you’ll have to write a proper SettingsFileManager.

If anything it should give you a good base to get started. But I wrote it primarily as a test to see what I know about ruby. Since it uses some semi-tricky stuff.

Hosted it on github too with some tests.

class Settings

  attr_accessor :settings

  def initialize(file_writer)
    @file_writer = file_writer
    read_settings_to_new_hash
  end

  def read_settings_to_new_hash
    @settings = fabricate_hash
    @settings.replace(@file_writer.read_keys)
  end

  def fabricate_hash
    InterceptedHash.new( &hash_saved_proc )
  end

  def hash_saved_proc
    Proc.new do |key, value|
      @file_writer.write_key(key, value)
    end
  end

  def method_missing(m, *args, &block)
    if @settings.has_key?(m) || args[0]
      if args[0]
        @settings[m.to_s.sub("=","").to_sym] = args[0]
      else
        @settings[m]
      end
    else
      raise "unknown setting"
    end
  end

end

# Not implemented. This should continue the logic to interact with whatever you want.
class SettingsFileManager
  def initialize(file)
    @file = file
  end

  # write the key and its value somewhere.
  def write_key(key, value)
    puts 'write_key', key, value
  end

  # should return hash of keys.
  def read_keys
    puts 'read_keys'
    Hash.new
  end
end

class InterceptedHash < Hash
  def initialize(&block)
    super
    @block = block
  end

  def store(key, value)
    super(key, value)
    @block.call(key, value)
  end

  def []=(key, value)
    store(key, value)
  end
end