Jifty::Manual::ObjectModel(3pm) 			User Contributed Perl Documentation			   Jifty::Manual::ObjectModel(3pm)

NAME

       Jifty::Manual::ObjectModel -- An overview of the Jifty object model

OVERVIEW

       Jifty applications are generally built in a similar way. There's no reason you need to use the model we've built, but we find it a
       reasonably OK way to do things.

       This document should serve as a roadmap to the Jifty class library, as well as an introduction to the way Jifty applications are put
       together.

       We start with the classes in your application and move on to the bits of Jifty itself.

       If you create a brand new application, let's call it "MyWeblog", and create one model class called "MyWeblog::Post", you'll end up with the
       following files and directories:

	   MyWeblog/
	       etc/
		   config.yml
	       lib/
		   MyWeblog/
		       Model/
			   Post.pm
		       Action/
	       bin/
		   jifty

	       web/
		   templates/
		   static/

	       t/
		   #some test files.

       At least that's the scaffolding Jifty creates for you. Behind the scenes, Jifty is actually doing a lot more. Rather than create a bunch of
       little "stub" classes and libraries for you, Jifty generates them on the fly. It's always possible to actually create these libraries when
       you need to customize the default behavior, but we work really hard to make sure you don't need to.

       Right now, Jifty is automatically creating libraries, static web pages and web templates.

       We're not 100% satisfied with how Jifty automatically creates web templates and static pages and are working to redesign that.

       The library you see when creating a Jifty app is:

       MyWeblog::Model::Post
	   "MyWeblog::Model::Post" describes the schema and business logic of your post class. It uses two namespaces,
	   "MyWeblog::Model::Post::Schema" that has actual column definitions and "MyWeblog::Model::Post" that contains the (optional) business
	   logic, access control and so on.

       That's it. But if you look carefully at "MyWeblog::Model::Post", you'll see the line:

	   use base qw/MyWeblog::Record/;

       How can that possibly work? There is no "MyWeblog::Record" class in your application. And Jifty, while it tries to be a comprehensive
       framework, draws the line somewhat short of including application-specific base classes for every application you might possibly contrive.

       The answer lies in Jifty::ClassLoader, a utility module Jifty uses to create the boring stuff for you when you need it.

       It'd certainly be possible for Jifty to create every class you might need as a file on disk when you first create your application (and
       indeed we may decide to do so if enough people yell at us), but when the stub classes we'd provide are just little shims that inherit from
       or call to the Jifty core, it doesn't make much sense to create them before you need them.  You could build a Jifty application without
       these shims by having your model classes inherit directly from Jifty::Record, but then you'll run into trouble the second you want to add
       application-specific code and have to go back and retrofit each and every one of your classes to use your new base class. It's a little
       thing, but one that can save you a bunch of pain and suffering later on.

       "MyWeblog::Record" is the first autogenerated class you'll run into but probably not the last. A full list of everything Jifty provides for
       your new application follows:

       You get one each of the these:

       MyWeblog::Record
	   This class is, as discussed above, a thin wrapper around Jifty::Record. You might choose to create your own "MyWeblog::Record" if you
	   want to build in custom access control by overriding "current_user_can" in Jifty::Record or want to implement methods that every model
	   class should have access to.

       MyWeblog::Collection
	   We haven't talked much about collections yet, but as their name implies, collections are bundles of Jifty::Record objects that match
	   some set of criteria. It's relatively uncommon that you'll want to override this, but if you want the rope, it's here.

       MyWeblog::Notification
	   "MyWeblog::Notification" is an app-specific implementation of the Jifty::Notification email driver. You might want to override this
	   class if you want to set an application-specific header or footer for all outgoing email.

       MyWeblog::Dispatcher
	   "MyWeblog::Dispatcher" is an application-specific "dispatcher" class that allows you to write code that runs when a client makes a
	   request to the server before Jifty runs actions or renders templates.  See Jifty::Dispatcher for more information about the dispatcher.

       MyWeblog::CurrentUser
	   Most every web application that grows past a personal hack eventually starts to provide personalization, require access control or
	   otherwise want to know who's currently in the driver's seat. The "current user" for an application is a first-class object in Jifty. To
	   get user-based authentication working out of the box, you'll have to override the default "MyWeblog::CurrentUser". (Out of the box, it
	   treats everyone as the same user.) We're working to generalize the authentication system we've used in a few Jifty apps so far to the
	   point where it feels "right" as a core Jifty component, but we're not quite there just yet.

	   Most of what you'll need to override in "MyWeblog::CurrentUser" is the "_init" function, which needs to load up an application-specific
	   model class that represents one of your users into its "user_object" accessor.  To make all this work, you'll also need an application-
	   specific "MyWeblog::Action::Login" and likely also a passel of user-management code.

	   (And yes, this is the topic of a future generalization and a future tutorial. At that point, a bunch of this documentation will be
	   extracted to Jifty::CurrentUser.)

       But wait! There's more!	You also get one each of these for your default model class:

       MyWeblog::Model::PostCollection
	   It's no fun having a weblog that only shows you one post at a time, is it?  Jifty provides you with default Jifty::Collection classes
	   for every Jifty::Record subclass in your model.  You get all the standard "limit", "order_by", "columns", paging support and so-on out
	   of the box, but sometimes when you're going to be getting collections matching certain criteria often, it makes sense to actually
	   create your own subclass and start dropping methods in.

       MyWeblog::Action::CreatePost, MyWeblog::Action::UpdatePost, MyWeblog::Action::DeletePost
	   One of Jifty's strengths is that it makes it easy to build applications by tying application-specific controller functions to your
	   model classes and intuiting what parameters they take by having a look inside the models.

	   For each class in your model, Jifty creates three actions, "Create","Update" and "Delete".  They're named, perhaps a bit
	   unadventureously, "MyWeblog::Action::CreatePost", "MyWeblog::Action::UpdatePost", "MyWeblog::Action::DeletePost" and inherit directly
	   from Jifty::Action::Record::Create, Jifty::Action::Record::Update and Jifty::Action::Record::Delete, respectively. Sometimes, it makes
	   sense to override these default actions when you want to change the behaviour of one or more of the actions.  One common use is to add
	   or remove AJAX validation or autocompletion for an argument or to change an argument's default value for webforms.  This, isn't,
	   however the place to start inserting business logic or access control. That belongs in your model class, which these wrappers will hand
	   things off to. By putting logic in your actions, you make your model classes less useful and run into trouble when you want to start
	   scripting your model outside a web environment.

       There's no reason you need to stick with these default "implementations" if they're not meeting your needs. Just create your own classes
       and Jifty will use your real classes instead.

perl v5.14.2							    2010-12-08					   Jifty::Manual::ObjectModel(3pm)