Introduce Null Object.

introduce-null-object/lib/after.rb

@@ -0,0 +1,37 @@
+class Post
+  attr_reader :id, :title, :body, :created_at
+  def initialize id, title, body, created_at
+    @id         = id
+    @title      = title
+    @body       = body
+    @created_at = created_at
+    @published = false
+  end
+
+  def self.find_and_publish id
+    # database operation to retrieve data. We'll simulate it for now.
+    post = POSTS.find { |post| post.id == id } || NullPost.new
+    post.publish
+  end
+
+  def publish
+    @published = true
+  end
+
+end
+
+class NullPost
+  def publish
+    # noop
+  end
+end
+
+POSTS = [
+  Post.new(
+    1,
+    "Introduce Null Object Pattern",
+    "Post body should be here",
+    Time.new(2013,01,25)
+  )
+]
+

introduce-null-object/lib/before.rb

@@ -0,0 +1,31 @@
+class Post
+  attr_reader :id, :title, :body, :created_at
+  def initialize id, title, body, created_at
+    @id         = id
+    @title      = title
+    @body       = body
+    @created_at = created_at
+    @published = false
+  end
+
+  def self.find_and_publish id
+    # database operation to retrieve data. We'll simulate it for now.
+    post = POSTS.find { |post| post.id == id }
+    post.publish unless post.nil?
+  end
+
+  def publish
+    @published = true
+  end
+
+end
+
+POSTS = [
+  Post.new(
+    1,
+    "Introduce Null Object Pattern",
+    "Post body should be here",
+    Time.new(2013,01,25)
+  )
+]
+

introduce-null-object/test/test.rb

@@ -1,5 +1,15 @@
-require 'minitest/spec'
 require 'minitest/autorun'
+require 'minitest/spec'
 
 require 'before' if ENV["BEFORE"]
 require 'after' unless ENV["BEFORE"]
+
+describe Post do
+  it "is publishable" do
+    Post.find_and_publish(1).must_equal true
+  end
+
+  it "does nothing if post is not found" do
+    Post.find_and_publish(0)
+  end
+end