DataMapper gem如何将应用程序逻辑和数据持久性分开？

Question

这是Ruby数据映射器的入门示例。但是，此示例如何说明将应用程序逻辑和数据持久性分开的datamapper的强大功能？

任何更好的例子都可以告诉我们，分离可以让我们更容易进行单元测试吗？

class Post
  include DataMapper::Resource

  property :id,         Serial    # An auto-increment integer key
  property :title,      String    # A varchar type string, for short strings
  property :body,       Text      # A text block, for longer string data.
  property :created_at, DateTime  # A DateTime, for any date you might like.
end


# create makes the resource immediately
@post = Post.create(
  :title      => "My first DataMapper post",
  :body       => "A lot of text ...",
  :created_at => Time.now
)

# Or new gives you it back unsaved, for more operations
@post = Post.new(:title => ..., ...)
@post.save                           # persist the resource

谢谢！