Now able to specify AR model + key on DataPatcher instanciation. Test…

…s cleanup. We're mostly done.

lib/data_patcher.rb

@@ -1,9 +1,19 @@
-require 'activesupport'
+require 'active_record'
+require 'active_support'
 
 class DataPatcher
+  attr_reader :model, :key, :patch
 
-  def analyze_record(key, attributes)
-    existing = Item.find_by_asin(attributes[key])
+  # model: activerecord class
+  # key: unique key accross all model instances
+  def initialize(model, key)
+    @model = model
+    @key = key
+    @patch = {}
+  end
+
+  def analyze_record(attributes)
+    existing = model.find(:first, :conditions => { key => attributes[key] })
     if existing
       existing_attributes = existing.attributes.dup.symbolize_keys.except(:id)
       diff = attributes.diff(existing_attributes)
@@ -19,14 +29,5 @@ def analyze_record(key, attributes)
     end
   end
 
-  # test commodity - remove ?
-  def analyze_records(key, records)
-    records.each { |record| analyze_record(key, record) }
-  end
-
-  def patch
-    @patch ||= {}
-  end
-
 end
 

spec/data_patcher_spec.rb

@@ -3,40 +3,29 @@
 describe DataPatcher do
 
   before(:each) do
-    @existing_item_1 = {
-                :title => "Mastering Data Warehouse Aggregates",
-                :summary => "The first book to provide in-depth coverage of star schema aggregates...",
-                :asin => "0471777099" }
-    @existing_item_2 = {
-                  :title => "The Data Warehouse ETL Toolkit",
-                  :summary => "The single most authoritative guide on the most difficult phase of building a data warehouse",
-                  :asin => "0764567578" }
-    @existing_items = [@existing_item_1, @existing_item_2]
-    Item.delete_all
-    Item.create!(@existing_item_1)
-    Item.create!(@existing_item_2)
-    @patcher = DataPatcher.new
-  end
-
-  def patcher
-    @patcher
+    load_fixture
+
+    @patcher = DataPatcher.new(Item, :asin)
+    # pre-load the patcher with all the existing data, so that we can simulate an addition or modification
+    @patcher.analyze_record(@existing_item_1)
+    @patcher.analyze_record(@existing_item_2)
   end
 
   it "provides an addition patch including the key and the attributes" do
-    patcher.analyze_records(:asin, @existing_items)
-    patcher.analyze_record(:asin, { :asin => "123", :title => "Hello", :summary => "The best of hello world" } )
-    patcher.patch.should == {
+    @patcher.analyze_record({ :asin => "123", :title => "Hello", :summary => "The best of hello world" } )
+
+    @patcher.patch.should == {
       :added => [{ :asin => "123", :title => "Hello", :summary => "The best of hello world" }]
     }
   end
 
   it "provides a modification patch including the key and updated attributes" do
-    patcher.analyze_records(:asin, @existing_items)
-    patcher.analyze_record(:asin, { 
+    @patcher.analyze_record( { 
       :asin => "0471777099", # key
       :title => "Mastering Data Warehouse Aggregates (Hard cover)", # changed data
       :summary => "The first book to provide in-depth coverage of star schema aggregates..."}) # unchanged data
-    patcher.patch.should == {
+
+    @patcher.patch.should == {
       :modified => [{ :asin => "0471777099", :title => "Mastering Data Warehouse Aggregates (Hard cover)"}]
     }
   end

spec/migrations/create_items.rb

@@ -5,10 +5,3 @@
   t.column :asin,    :string, :null => false
   # TODO - add timestamps here ?
 end
-
-Item.create :title => "Mastering Data Warehouse Aggregates",
-            :summary => "tThe first book to provide in-depth coverage of star schema aggregates...",
-            :asin => "0471777099"
-Item.create :title => "The Data Warehouse ETL Toolkit",
-            :summary => "The single most authoritative guide on the most difficult phase of building a data warehouse",
-            :asin => "0764567578"

spec/spec_helper.rb

@@ -2,6 +2,7 @@
 require 'spec'
 
 $LOAD_PATH.unshift(File.dirname(__FILE__))
+$LOAD_PATH.unshift(File.dirname(__FILE__) + "/../lib")
 
 require 'data_patcher'
 
@@ -28,3 +29,16 @@
   require file.gsub(/\.rb$/, '')
 end
 
+def load_fixture
+  @existing_item_1 = {
+              :title => "Mastering Data Warehouse Aggregates",
+              :summary => "The first book to provide in-depth coverage of star schema aggregates...",
+              :asin => "0471777099" }
+  @existing_item_2 = {
+                :title => "The Data Warehouse ETL Toolkit",
+                :summary => "The single most authoritative guide on the most difficult phase of building a data warehouse",
+                :asin => "0764567578" }
+  Item.delete_all
+  Item.create!(@existing_item_1)
+  Item.create!(@existing_item_2)
+end