Added find_by_param methods and tests

init.rb

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+require 'find_by_param'
+ActiveRecord::Base.send(:extend, FindByParam::ClassMethods)

lib/find_by_param.rb

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+module FindByParam
+  module ClassMethods
+    def define_find_param(param, options={})
+      param = param.to_s
+      options[:raise_on_not_found] ||= false
+      if column_names.include?(param)
+        write_inheritable_attribute :find_parameter, param
+        write_inheritable_attribute :find_param_options, options
+        bl = lambda do |args|
+          results = send("find_by_#{read_inheritable_attribute(:find_parameter)}", *args)
+          raise ActiveRecord::RecordNotFound if options[:raise_on_not_found] && (results.nil? or (results.is_a?(Array) && results.empty?))
+          return results
+        end
+        self.class.send(:define_method, 'find_by_param', &bl)
+      else
+        raise StandardError
+      end
+      self.send(:include, FindByParam::InstanceMethods)
+    end
+  end
+
+  module InstanceMethods
+    def to_param
+      self.send(self.class.read_inheritable_attribute(:find_parameter))
+    end
+  end
+end

test/find_by_param_test.rb

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+require File.join(File.dirname(__FILE__), 'test_helper')
+
+class FindByParamTest < Test::Unit::TestCase
+  def setup
+    BlogPost.create(:slug => 'adam-west', :title => 'Adam West')
+    BlogPost.create(:slug => 'burt-ward', :title => 'Burt Ward')
+    BlogPost.send(:define_find_param, 'slug')
+  end
+
+  def teardown
+    BlogPost.delete_all
+  end
+
+  def test_plugin_loaded_correctly
+    assert BlogPost.respond_to?(:find_by_param)
+  end
+
+  def test_returns_valid_data
+    bp = BlogPost.find(:first, :conditions => 'slug = "adam-west"')
+    assert_equal BlogPost.find_by_param('adam-west'), bp
+  end
+
+  def test_can_define_find_parameter
+    BlogPost.send('define_find_param', 'title')
+    bp = BlogPost.find(:first, :conditions => {:slug => 'adam-west'})
+    assert_equal BlogPost.find_by_param('Adam West'), bp
+  end
+
+  def test_correctly_goes_to_param
+    bp = BlogPost.find(:first, :conditions => {:slug => 'adam-west'})
+    assert_equal bp.to_param, 'adam-west'
+  end
+end

test/test_helper.rb

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+$LOAD_PATH.unshift 'lib/'
+
+require 'rubygems'
+require 'multi_rails_init'
+require 'action_controller/test_process'
+require 'test/unit'
+require 'find_by_param'
+
+begin
+  require 'redgreen'
+rescue LoadError
+  nil
+end
+
+RAILS_ROOT = '.'    unless defined? RAILS_ROOT
+RAILS_ENV  = 'test' unless defined? RAILS_ENV
+
+
+ActiveRecord::Base.send(:extend, FindByParam::ClassMethods)
+ActiveRecord::Base.establish_connection(:adapter => "sqlite3", :dbfile => ":memory:")
+ActiveRecord::Base.logger = Logger.new(STDOUT)
+
+ActiveRecord::Schema.define(:version => 1) do
+  create_table :blog_posts do |t|
+    t.column :slug, :string
+    t.column :title, :string
+  end
+end
+
+class BlogPost < ActiveRecord::Base
+  define_find_param :slug
+end