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Jifty::Manual::ObjectMUser(Contributed Perl DocumJifty::Manual::ObjectModel(3)

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 v5.32.0			  2013-01-29	 Jifty::Manual::ObjectModel(3)

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