[Jifty-commit] r429 -

jifty-commit at lists.jifty.org jifty-commit at lists.jifty.org
Fri Dec 30 11:22:59 EST 2005

Author: jesse
Date: Fri Dec 30 11:22:58 2005
New Revision: 429

   /   (props changed)

 r21945 at truegrounds:  jesse | 2005-12-30 15:28:07 +0100
 * Actually described how Jifty::ClassLoader works its magic, so that users can build apps that use actions

Modified: jifty/trunk/lib/Jifty/Manual/ObjectModel.pod
--- jifty/trunk/lib/Jifty/Manual/ObjectModel.pod	(original)
+++ jifty/trunk/lib/Jifty/Manual/ObjectModel.pod	Fri Dec 30 11:22:58 2005
@@ -2,9 +2,187 @@
 Jifty::Manual::ObjectModel -- An overview of the Jifty object model
-=head1 CONTENT
+=head1 OVERVIEW
+Jifty applications are generally built in a similar way. There's no reason
+you I<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 I<your> application and move on to the bits
+of Jifty itself.
+If you create a brand new application, let's call it C<MyWeblog>, and
+create one model class called C<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 I<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 autocreating libraries, static web pages and web templates.
+We're not 100% satisfied with how Jifty autocreates web templates and static pages
+and are working to redesign that.
+The library you I<see> when creating a Jifty app is:
+=item MyWeblog::Model::Post
+C<MyWeblog::Model::Post> describes the schema and business logic of your
+post class. It uses two namespaces, C<MyWeblog::Model::Post::Schema>
+that has actual column definitions and C<MyWeblog::Model::Post> that
+contains the (optional) business logic, access control and so on.
+That's it. But if you look carefully at C<MyWeblog::Model::Post>, you'll see
+the line:
+    use base qw/MyWeblog::Record/;
+How can that possibly work? There is no C<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 L<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.
+C<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:
+=item MyWeblog::Record
+This class is, as discussed above, a thin wrapper around
+L<Jifty::Record>. You might choose to create your own MyWeblog::Record
+if you want to build in custom access control by overriding
+L<Jifty::Record/current_user_can> or want to implement methods that
+every model class should have access to.
+=item MyWeblog::Collection
+We haven't talked much about collections yet, but as their name implies,
+collections are bundles of L<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.
+=item MyWeblog::Notification 
+jC<MyWeblog::Notification> is an app-specific of the
+C<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.
+=item 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 C<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 C<MyWeblog::CurrentUser> is the
+C<_init> function, which needs to load up an application-specific model
+class that represents one of your users into its C<user_object> accessor.
+To make all this work, you'll also need an application-specific C<Login>
+L<Jifty::Action> subclass and likely also a passel of user-management
+(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 L<Jifty::CurrentUser>.)
+But wait! There's more!  You also get one each of these for your default
+model class:
+=item 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 L<Jifty::Collection> classes
+for every L<Jifty::Record> subclass in your model.  You get all the
+standard C<limit>, C<order_by>, C<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.
+=item 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 C<::Record> class in your model, Jifty creates three
+actions, C<Create>,C<Update> and C<Delete>.  They're named,
+perhaps a bit unadventureously, C<MyWeblog::Action::CreatePost>,
+C<MyWeblog::Action::UpdatePost>, C<MyWeblog::Action::DeletePost>
+and inherit directly from C<Jifty::Action::Record::Create>,
+C<Jifty::Action::Record::Update> and C<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.

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