Eoraptor Extracts - "Prepares.rb" - Ninjas on a Penny Farthing

Just a simple one to start off today - This is a piece of code I've reused quite a few times and it's really saved me a lot of coding time retyping the same thing. In essence, prepares is a single drop in file for rails that adds a few niceties - basically preparing a model instance (via find) and storing it in an instance variable.

For example, if you want to prepare the model Post in the current controller on a certain set of actions, you may use this -

prepares :post, :only => [:show, :edit, :update, :destroy, :publish]

You have :only and :except options which can be passed straight into the before filter it builds. Other options include:

:instance_var - the alternative instance variable name to use
:params_key - what params attribute to use
:if - a string (same as ruby code) which will be called if passed in e.g. a method (:action_name) - it's eval'ed
:model - An alternate model to use; can either be a class (on which to_s is called for the name) or a symbol e.g. :blog_post -> BlogPost

There are no tests / documentation for it other than this (it's something I need to work on) but it in use on this blog. Oh, if you pick up an error, let me know - I chopped out some parts of it at the last minute.

Using it

Just add prepares.rb to your lib subdirectory of rails with this code; then add:

include Prepares::ControllerMixin

to your application controller / whichever controllers you want to use it.

The Source

Use it, even if your name isn't Luke and it isn't "The Force".

# prepares.rb - Copyright Darcy R. Laycock, 2008
# http://blog.ninjahideout.com
# Use as you want but please keep this header up top.
module Prepares
  
  module ControllerMixin
    def self.included(parent)
      parent.class_eval do
        extend Prepares::ClassMethods
        include Prepares::InstanceMethods
      end
    end
  end
  
  module ClassMethods
    
    def prepares(name, opts = {})
      raise ArgumentError unless opts.is_a?(Hash)
      opts.assert_valid_keys(:instance_var, :model, :except, :only, :params_key, :if)
      params_key = opts[:params_key] || :id
      instance_var_name = "@#{(opts[:instance_var] || name).to_s.gsub(/^[@]+/, "")}"
      conditionals = opts.delete(:if) || nil
      pmodel = get_prepares_model(opts[:model] || name)
      method_name = :"prepares_#{name.to_s.underscore}"
      method =  "def #{method_name}\n"
      method