Nested Model Forms

The most popular request on our new Feedback site was for the ability to easily manage multiple models in a single form. Thankfully Eloy Duran has a patch that does just this. But before we roll it into rails 2.3 we want to get some more feedback from you guys. Eloy's written this brief introduction to the patch, so take a look, and add any feedback you have to the lighthouse ticket.

In Rails it has always been a little tricky to create a single form for both a model and its associations. Last summer, the :accessible option was committed as a first stab at a unified solution for dealing with nested models. However, this feature was pulled before the 2.2 release because it only supported nested models during object creation.

The resulting discussion on the core mailing list and our need for mass assignment have resulted in this patch for ticket #1202 which is now up for scrutinizing.

Since this is a rather large patch we would like to invite you to give it a try. Please report any issues or give feedback about the patch in general. We are especially interested to know how the provided solutions work for applications that allow deletion of nested records through their forms.

Below I'll give a quick tour on what the patch does and how to use it so you have no excuse not to give it a try.

Get the patch

Start by creating a new application:

$ mkdir -p nested-models/vendor
$ cd nested-models/vendor

Vendor your Rails branch with the nested models patches:

$ git clone git://github.com/alloy/rails.git
$ cd rails
$ git checkout origin/normalized_nested_attributes
$ cd ../..
$ ruby vendor/rails/railties/bin/rails .

An example of nested assignment

Suppose you have a project model with associated tasks:

class Project < ActiveRecord::Base
  has_many :tasks

  validates_presence_of :name
end
class Task < ActiveRecord::Base
  belongs_to :project

  validates_presence_of :name
end

Now consider the following form which allows you to simultaneously create (or edit) a project and its tasks:

<form>
  <div>
    <label for="project_name">Project:</label>
    <input type="text" name="project_name" />
  </div>

  <p>
    <label for="task_name_1">Task:</label>
    <input type="text" name="task_name_1" />
    <label for="task_delete_1">Remove:</label>
    <input type="checkbox" name="task_delete_1" />
  </p>

  <p>
    <label for="task_name_2">Task:</label>
    <input type="text" name="task_name_2" />
    <label for="task_delete_2">Remove:</label>
    <input type="checkbox" name="task_delete_2" />
  </p>
</form>

Before the patch

Before this patch you would have to write a template like this:

<% form_for @project do |project_form| %>
  <div>
    <%= project_form.label :name, 'Project name:' %>
    <%= project_form.text_field :name %>
  </div>

  <% @project.tasks.each do |task| %>
    <% new_or_existing = task.new_record? ? 'new' : 'existing' %> 
    <% prefix = "project[#{new_or_existing}_task_attributes][]" %> 
    <% fields_for prefix, task do |task_form| %>
      <p>
        <div>
          <%= task_form.label :name, 'Task:' %>
          <%= task_form.text_field :name %>
        </div>

        <% unless task.new_record? %>
          <div>
            <%= task_form.label :_delete, 'Remove:' %>
            <%= task_form.check_box :_delete %>
          </div>
        <% end %>
      </p>
    <% end %>
  <% end %>

  <%= project_form.submit %>
<% end %>

The controller is pretty much your average restful controller. The Project model however needs to know how to handle the nested attributes:

class Project < ActiveRecord::Base
  after_update :save_tasks

  def new_task_attributes=(task_attributes)
    task_attributes.each do |attributes|
      tasks.build(attributes)
    end 
  end

  def existing_task_attributes=(task_attributes)
    tasks.reject(&:new_record?).each do |task|
      attributes = task_attributes[task.id.to_s]
      if attributes['_delete'] == '1'
        tasks.delete(task)
      else
        task.attributes = attributes
      end
    end
  end

  private

  def save_tasks
    tasks.each do |task|
      task.save(false)
    end
  end

  validates_associated :tasks
end

The code above is based on Ryan Bates' complex-form-examples application and from the Advanced Rails Recipes book.

After this patch

First you tell the Project model to accept nested attributes for its tasks:

class Project < ActiveRecord::Base
  has_many :tasks

  accept_nested_attributes_for :tasks, :allow_destroy => true
end

Then you could write the following template:

<% form_for @project do |project_form| %>
  <div>
    <%= project_form.label :name, 'Project name:' %>
    <%= project_form.text_field :name %>
  </div>

  <!-- Here we call fields_for on the project_form builder instance.
       The block is called for each member of the tasks collection. -->
  <% project_form.fields_for :tasks do |task_form| %>
      <p>
        <div>
          <%= task_form.label :name, 'Task:' %>
          <%= task_form.text_field :name %>
        </div>

        <% unless task_form.object.new_record? %>
          <div>
            <%= task_form.label :_delete, 'Remove:' %>
            <%= task_form.check_box :_delete %>
          </div>
        <% end %>
      </p>
    <% end %>
  <% end %>

  <%= project_form.submit %>
<% end %>

As you can see this is much more concise and easier to read.

Granted, the template for this example is only slightly shorter, but it's easy to imagine the difference with more nested models. Or if the Task model had nested models of its own.

Validations

Validations simply work as you'd expect; #valid? will also validate nested models, #save(false) will save without validations, etc.

The only thing to note is that all error messages from the nested models are copied to the parent errors object for error_messages_for. This will probably change in the future, as discussed on the ticket, but that's outside of the scope of this patch.

Let's look at an example where Task validates the presence of its :name attribute:

>> project = Project.first
=> #<Project id: 1, name: "Nested models patches", created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15", author_id: 1>

>> project.tasks
=> [#<Task id: 1, project_id: 1, name: "Write 'em", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">,
#<Task id: 2, project_id: 1, name: "Test 'em", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">,
#<Task id: 3, project_id: 1, name: "Create demo app", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">,
#<Task id: 4, project_id: 1, name: "Scrutinize", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">]

>> project.tasks.second.name = "" 
=> "" 

>> project.valid?
=> false

>> project.errors
=> #<ActiveRecord::Errors:0x23e4b10 @errors={"tasks_name"=>["can't be blank"]}, @base=#<Project id: 1, name: "Nested models patches", …, author_id: 1>>

Transactions

By now you are probably wondering about the consistency of your data when validations passes but saving does not. Consider this Author model which I have rigged to raise an exception after save:

class Author < ActiveRecord::Base
  has_many :projects

  after_save :raise_exception

  def raise_exception
    raise 'Oh noes!'
  end
end

Here's the Project data before an update:

>> project = Project.first
=> #<Project id: 1, name: "Nested models patches", created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15", author_id: 1>

>> project.tasks
=> [#<Task id: 1, project_id: 1, name: "Write 'em", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">,
#<Task id: 2, project_id: 1, name: "Test 'em", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">,
#<Task id: 3, project_id: 1, name: "Create demo app", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">,
#<Task id: 4, project_id: 1, name: "Scrutinize", due_at: nil, created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">]

>> project.author
=> #<Author id: 1, name: "Eloy", created_at: "2009-01-22 11:17:15", updated_at: "2009-01-22 11:17:15">

Now let's delete the first Task and change the name of the second Task:

>> project.tasks_attributes = { "1" => { "_delete" => "1" }, "2" => { "name" => "Who needs tests anyway?!" } }
=> {"1"=>{}, "2"=>{"name"=>"Who needs tests anyway?!"}}

>> project.tasks.first.marked_for_destruction?
=> true

>> project.tasks.forty_two
=> nil # Oops, I meant #second of course… ;)

>> project.tasks.second.name
=> "Who needs tests anyway?!" 

Finally, let's try to save the Project instance:

>> project.save
RuntimeError: Oh noes!
  from /Users/eloy/code/complex-form-examples/app/models/author.rb:9:in `raise_exception_if_needed'

An exception was raised while saving one of the nested models. Now let's see what happened to the data:

SQL (0.1ms)   BEGIN
Task Destroy (0.3ms)   DELETE FROM `tasks` WHERE `id` = 1
Task Update (0.2ms)   UPDATE `tasks` SET `updated_at` = '2009-01-22 11:22:23', `name` = 'Who needs tests anyway?!' WHERE `id` = 2
SQL (17.0ms)   ROLLBACK

As you can see, all changes were rolled back. Both updates as well as the removal of records marked for destruction all happen inside the same transaction.

As with any transaction, the attributes of the instance that you were trying to save will not be reset. This means that after this failed transaction the first task is still marked for destruction and the second one still has the new name value.

Conclusion

This patch allows you to create forms for nested model as deep as you would want them to be. Creating, saving, and deleting should all work transparently and inside a single transaction.

Please test this patch on your application, or take a look at my fork of Ryan's complex-form-examples which uses this patch.

Your feedback is much appreciated. However, keep in mind that we can't possibly satisfy everyone's needs all at once. Please suggest additional features or major changes as a separate ticket for after the patch has been applied. The goal is to fix the bugs in this patch first so we all have a clean foundation to build on.

On a final note, I would like to thank David Dollar for the original :accessible implementation, Fingertips (where I work) for sponsoring the time that has gone into this patch, Manfred Stienstra for extensive help on the documentation, and in no particular order Lance Ivy, Michael Koziarski, Ryan Bates, Pratik Naik and Josh Susser for general discussion.

RailsConf 2009: Viva Las Vegas!

RailsConf 2009 is now open for registration. We’re going to Las Vegas this year. More precisely the Las Vegas Hilton from May 4th through 7th. It’s going to be a party for sure.

There has been such an incredible amount of activity since last year. We have the merging of Merb back into Rails, Rails 2.2 and 2.3, and probably a good showing of Rails 3.0. So we should be absolutely packed for great content this year.

It’s going to be hard to top 2008, though. I really thought that was a fantastic show. Great lineup of proposals, great speakers, and a great sense of community. Which is pretty hard to do when you have almost 2,000 people gathered. So we’ll try extra hard this year to outdo it.

So I hope to see many familiar and new faces this year. We have early registration open until March 16th, so you can save up to $200 by getting it done early.

Don’t forget to get your speaker proposal in either. You have until February 17th.

See you all in Vegas!

This Week in Edge Rails

January 17, 2009 -January 23, 2009

Edge Rails saw 28 commits this week. Here’s a look at some of them. As always, you’ll want to go back to the GitHub commit list if you want to look at every single change. As we near 2.3, many of the commits we’re seeing are bug fixes rather than new features, and I’m generally not covering those here.

More Rack Middleware

The Rack-ification of Rails continues, with more and more Rails code being refactored into Rack middleware. This week, parsers for XML, JSON, and YAML got moved into ActionController::ParamsParser middleware. In the long run, this sort of refactoring will make many of Rails services open to other Rack clients, without every framework needing to reinvent all of the same wheels. commit

Deprecations

If you were one of the people who got used to running script/performance/request to look at performance based on integration tests, you need to learn a new trick: that script has been removed from core Rails now. But don’t worry if you depend on it. There’s a new request_profiler plugin that you can install to get the exact same functionality back.

Also on the deprecation list is ActionController::Base#session_enabled?, which now returns a deprecation warning when you try to use it. But given that sessions are lazy-loaded now, to disable them all you need to do to disable them is to not use them in the first place. commit

Local Caching for All!

Last week, we saw an improvement to caching performance when using MemCacheStore, keeping a local request cache to avoid redundant reads. This week, that work was refactored so that it can be used with any remote store. commit

This Week in Edge Rails

January 10, 2009 -January 16, 2009

24 commits for edge Rails this week (with one patch ported over to the 2.2 branch as well). If you want a pre-release look at Rails 2.3, this is a fine time to install a copy of edge, if you’re not already there. It’s plenty stable enough for test sites, though there are a few rough patches yet.

Nested Transactions in Active Record

Several people contributed to a big patch that gives us nested transactions in Active Record, a much-requested feature. Now you can write code like this:


User.transaction do
    User.create(:username => 'Admin')
    User.transaction(:requires_new => true) do
      User.create(:username => 'Regular')
      raise ActiveRecord::Rollback
    end
  end
  
  User.find(:all)  # => Returns only Admin

Nested transactions let you rollback an inner transaction without affecting the state of the outer transaction. If you want a transaction to be nested, you must explicitly add the :requires_new option; otherwise, a nested transaction simply becomes part of the parent transaction (as it does currently on Rails 2.2). Under the covers, nested transactions are using savepoints, so they’re supported even on databases that don’t have true nested transactions. There is also a bit of magic going on to make these transactions play well with transactional fixtures during testing. commit

MemCacheStore Enhancements

Nahum Wild contributed some work that (inspired by his spandex_mem_cache_store plugin) that enhances the performance of Rails when using MemCacheStore. The basic idea is to keep a per-request local cache of requests sent to MemCacheStore, cutting down on unnecessary reads and leading to better site performance. commit

Making Active Record Callbacks behave

You may recall the spot in the Active Record documentation that says “If a before_* callback returns false, all the later callbacks and the associated action are cancelled.” What you may not know is that this is actually broken in the current version of Rails: if you cancel a before_update or before_create callback, the after_save callbacks still run. In Rails 2.3, this will behave the way that the documentation says it does. commit

Fractional seconds for TimeWithZone

The Time and TimeWithZone classes include an xmlschema method to return the time in an XML-friendly string. As of this week, TimeWithZone supports the same argument for specifying the number of digits in the fractional second part of the returned string that Time does:


>> Time.zone.now.xmlschema(6)
=> "2009-01-16T13:00:06.13653Z"

commit

JSON Key Quoting

If you look up the spec on the “json.org” site, you’ll discover that all keys in a JSON structure must be strings, and they must be quoted with double quotes. As of this week, Rails does the right thing here, even with numeric keys. commit

Test Refactoring

Josh Peek spent some time refactoring various tests inside of Action Pack, including those for query string parsing, JSON parameter parsing, XML parameter parsing, multipart parameter parsing, and URL-encoded parameter parsing. While you won’t see any new functionality as a result of this work, it’s worth shining a spotlight on the often-thankless cleanup that keeps the Rails code in good shape.

Changes to Object#try

After some discussion, the semantics of Object#try have changed slightly: it now raises NoMethodError on private methods and always returns nil if the object is nil. commit

Rails Documentation Projects

With the recent revitalization of the Rails Wiki project, we’re seeing people ask how the various pieces of Rails documentation fit together. I thought it might be useful to lay out how the Rails Activists see everything fitting together as we move forward.

Rails is a large and mature framework, with a lot of functionality – and with the Merb merger, there will be even more to learn in the future. As such, it presents challenges for developers at all levels trying to understand how to use Rails effectively. There are many resources to help with the learning process, including commercial books and magazines, screencasts and podcasts, tutorials, blog entries, and training courses. But there is also a series of official written documentation projects.

There’s no such thing as one-size-fits-all documentation. Different developers bring different skill sets, backgrounds, and levels of professional maturity to learning Rails. There are at least four levels of official documentation, overlapping but serving different needs:

  • Inline documentation, with comments within the code itself (that you can see by running rake doc:rails within any Rails project).
  • Rails Guides
  • Rails Book (a new project for Rails 3.0)
  • Rails wiki

Although at first glance there appears to be substantial overlap, our feeling is that the each of these projects occupies a distinct (and valuable) niche.

RDoc

  • Provides immediate help for syntax questions
  • Maintained by the actual core developers and generally up-to-date

Rails Guides:

  • Provides focused “how to” help for particular problem domains
  • Target the mid-level developer, possibly with Rails experience
  • Have a large amount of existing high-quality material
  • Are already being continuously revised to track changes in edge Rails
  • Can include version-specific tutorial code samples
  • Can be delivered as a part of core Rails to provide “guidance at your fingertips” for new developers

Rails Book:

  • Provides high-level architectural guidance and overview of how the pieces fit together
  • Digs into the philosophy of the “Rails Ways”, so readers can understand why the framework works the way it does
  • Targets the developer new to Rails or those wanting to go from the “trees” to the “forest” view
  • Offers help in conceptualizing Rails and choosing between alternative modules (ORMs, routing DSLs, etc.) in the Rails 3 timeframe
  • Can draw on the Merb experience in simultaneous translation and pulling in contributions from many writers
  • Largely version independent
  • Gives a structured path through end-to-end documentation in a way that standalone Guides do not

Rails Wiki

  • Community-driven documentation that can respond rapidly to new software and new questions
  • A good repository to links to external information
  • Potentially a showcase for Rails itself in the underlying software
  • A place to put the accumulated community knowledge, even the pieces that are not often needed

It’s important to note that we don’t see these four projects as entirely separate efforts that have no interaction with one another. In particular, it seems likely that the Book will link to the Guides for those seeking additional detail, while the Guides will link to the Book for those seeking additional high-level guidance. We also anticipate that the wiki will point readers to both Guides and Book (as well as to other sources of information).

So, what can you do to get involved? If you’re a writer, translator, or editor, any of these documentation projects would love to have your help:

  • To contribute to the RDoc, write a Rails patch with good comments or check out the docrails project.
  • To help the Rails Guides, get in touch with Pratik Naik or Mike Gunderloy, or drop by the #docrails channel on IRC freenode.
  • To get involved with the Rails Book, contact Matt Aimonetti.
  • To add to the Rails Wiki, join the rubyonrails-wiki group.

Activist Status & Wiki Project

So last week we were announced as activists, but what have we been doing? I’m sure there are some wondering, so here is our first report. Read on for news of our first big project, what each of us is working on, and how you can help today.

Firstly, we’ve been very pleased by the number of people who are actively interested in helping us improve the Rails ecosystem. Your input through UserVoice, the Activism Mailing List, Twitter, e-mail, and instant messages has been inspiring (and a bit overwhelming!). We listened, and one of the most popular requests revolved around the Wiki.

The Rails Wiki Reform

The Rails Wiki is in poor shape, for many reasons and it’s not one person’s fault. The good news is that our first major project is going to be revitalizing the wiki. To get our engines started, we’re forming a dedicated team to shape it into something the Rails community can be proud of.

If you’re interested in helping, simply join the Ruby on Rails Wiki Google Group. After you join, you’ll find a note on the group from Matt Aimonetti with more details.

What we’re doing

All of the Activists are busy with projects that fall under the general heading of “helping Rails.” Here’s a sampling of what we’re up to:

Gregg Pollack

Matt Aimonetti

  • Putting together Case Studies.
  • Investigating the current state of the Rails wiki and possibilities.
  • Working on the Merb book (yes, Merb projects help Rails too).

Ryan Bates

  • Doing Railscasts.com.
  • Creating a Screencast application for aggregating Rails screencasts all into one feed on the RubyOnRails.org website.

Mike Gunderloy

  • Covering This Week in Edge Rails on the official Rails blog.
  • Working with Chad Woolley to improve the Rails CI server, including builds across multiple versions of Ruby and JRuby.
  • Providing user support via #rubyonrails and #rails-activism on IRC freenode.
  • Posting daily link roundups pointing to things of interest to Rails developers.

Other Stuff You Can Do

If you’re asking “What can I do today to help Ruby on Rails?”, aside from joining one of our mailing lists and collaborating with us, here are a few items that come to mind:

  1. Contact Matt Aimonetti if you think you have a good Case Study on Rails.
  2. Go to RubyForum or IRC and help new Rails developers.
  3. Go to your local Ruby Users Group, or start one.
  4. Go to a Rails related conference.
  5. The next time you tackle a hard problem in your rails app, write a blog entry.
  6. Take one of your Rails Libraries/Modules, and turn it into a Gem or Plugin.
  7. If you’re surfing Rails blog articles and you find one that is outdated leave a comment or let the author know the content should be updated or marked as obsolete.

Flickr Credits: Big Red Button Okinawa-Churaumi Aquarium marbles

This Week in Edge Rails

January 3, 2009 -January 9, 2009

It was a pretty light week for the edge Rails tree: about 20 commits. We’re starting to see things coalesce for a 2.3 release, though there’s no official release date yet. Here’s some of the highlights of what’s been going on.

AssetTag Timestamp Caching

You’re likely familiar with Rails’ practice of adding timestamps to static asset paths as a “cache buster.” This helps ensure that stale copies of things like images and stylesheets don’t get served out of the user’s browser cache when you change them on the server. You can now modify this behavior with the cache_asset_timestamps configuration option for Action View. If you enable the cache, then Rails will calculate the timestamp once when it first serves an asset, and save that value. This means fewer (expensive) file system calls to serve static assets – but it also means that you can’t modify any of the assets while the server is running and expect the changes to get picked up by clients. commit

Object#tap Backport

Object#tap is an addition to Ruby 1.9 and 1.8.7 that is similar to the returning method that Rails has had for a while: it yields to a block, and then returns the object that was yielded. Rails now includes code to make this available to older versions of Ruby as well. commit

Rack Version Bump

During the week, the Rack project released version 0.9 and Rails was quick to respond – the required version of Rack for Rails is now 0.9. So, if you’re running on edge, it’s time to update your gems. commit

Continuous Integration Setup

If you’re interested in setting up your own continuous integration server to build the Rails source, the embedded instructions have been updated with the latest requirements and clarifications. Even if you want a CI server for something else, they’re worth looking at, as they’ll get you from zero to a running cc.rb instance very quickly. commit

Announcing the Rails activists

Railway station crowd

Bringing Rails and Merb together is about more than just merging the respective code. We’re also picking up the best ideas from both communities beyond the code. Following on Merb’s success in offering a strong evangelism effort, we’re pleased to announce the creation of the Rails activists:

The mission of the Rails activists is to empower and support the worldwide network of Ruby on Rails users. We do this by publicizing Rails, making adoption easier, and enhancing developer support.

At launch, we’ve identified seven areas where the Rails activists can contribute to the Rails ecosystem:

  • Public Relations with media of all sizes
  • Ombudsman work to ensure good user-to-user support
  • Community Leadership at events and conferences
  • Media Organization to help create good promotional opportunities
  • Website maintenance
  • Documentation efforts
  • Developer support

The initial members of the Rails activists are Gregg Pollack, Matt Aimonetti, Ryan Bates, and Mike Gunderloy. But we can’t do all this alone, nor do we want to! Our vision includes a large and vibrant Rails network composed of other activists, bloggers, event hosts, authors, and developers. Our intent is to provide connections, resources, and support to help the entire ecosystem to grow. To start things off, we’re bringing in a lot of our own projects, including videos, screencasts, case studies, Rails documentation, and more – we’re a working group, and we hope you’ll work with us.

If you have ideas about improving the Rails community, projects you want to participate in, or are just looking for ways to get involved, get in touch with us! There are a lot of ways to do that:

We look forward to hearing from you!

For additional perspectives from the activists, see the posts by Gregg Pollack, Matt Aimonetti, and Mike Gunderloy.

Photo by Flickr user caravinagre

This Week in Edge Rails

December 27, 2008-January 2, 2009

Happy New Year! Apparently the Rails core team was not doing too much partying to end the old year: we had 35 commits hit the edge tree, and some of them involved very substantial work. Here’s my weekly overview of some of the most visible and significant changes.

Optimization of respond_to

In some of the first fruits of the Rails-Merb team merger, Yehuda Katz took a look at the respond_to method, which is of course heavily used in many Rails applications to allow your controller to format results differently based on the MIME type of the incoming request. After eliminating a call to method_missing and some profiling and tweaking, he reports an 8% improvement in the number of requests per second served with a simple respond_to that switches between three formats. The best part? No change at all required to the code of your application to take advantage of this speedup. commit commit

If you want a preview of what else to expect from Rails 3, you might want to dip into Yehuda’s own fork of the Rails tree; I’ll be covering these changes as they make their way back into the master copy of edge Rails.

Dynamic Scopes for Active Record

You know about dynamic finders in Rails (which allow you to concoct methods like find_by_color_and_flavor on the fly) and named scopes (which allow you to encapsulate reusable query conditions into friendly names like currently_active). Well, now you can have dynamic scope methods. The idea is to put together syntax that allows filtering on the fly and method chaining. For example:


Order.scoped_by_customer_id(12)
Order.scoped_by_customer_id(12).find(:all, 
  :conditions => "status = 'open'")
Order.scoped_by_customer_id(12).scoped_by_status("open")

There’s some further discussion of this over on Ryan Daigle’s blog. commit

Other Active Record Updates

There were a few changes going on in Active Record this week. A trio of commits cleaned up some behavior of associations when the :primary_key option is specified. commit commit commit

On another front, ActiveRecord::Base#new_record? now returns false rather than nil when confronted with an existing record. While there was some discussion of the wisdom of this change, the consensus seems to be that it can’t hurt and might make things less surprising for some developers. commit

HTTP Digest Authentication

Rails now has built-in support for HTTP digest authentication. To use it, you call authenticate_or_request_with_http_digest with a block that returns the user’s password (which is then hashed and compared against the transmitted credentials):


class PostsController < ApplicationController
  Users = {"dhh" => "secret"}
  before_filter :authenticate
  
  def secret
    render :text => "Password Required!"
  end

  private
  def authenticate
    realm = "Application"
    authenticate_or_request_with_http_digest(realm) do |name|
      Users[name]
    end
  end
end

commit

Multiple Conditions for Callbacks

When using Active Record callbacks, you can now combine :if and :unless options on the same callback, and supply multiple conditions as an array:


before_save :update_credit_rating, :if => :active, 
  :unless => [:admin, :cash_only]

commit

Testing and continuous integration

A little flurry of activity cleaned up some loose ends in our testing strategy for Rails itself. This included not running symlink tests on Windows, adding test coverage to Rails::TemplateRunner, removing some assumptions in various tests, and getting the FCGI and sqlite2 tests working again. This is all part of a longer-term effort to make the Rails continuous integration server more useful moving forward. As you’ll see if you peek at the current build status, we’re not quite there yet, but we’re getting close.

By the way, if you want to set up your own CI server for Rails, there are instructions right in the source code.

Code Comments for Metaprogramming

One side effect of the changes to respond_to is that people really liked the inline comments that make the intent of the class_eval code clear. As a result, we now have similar comments throughout the Rails source code. For example:


def #{method_name}     # def year
  time.#{method_name}  #   time.year
end                    # end

If you’re just using Rails, you’ll never see these comments – but if you’re helping to maintain and improve the framework, you’ll appreciate them. commit

This Week in Edge Rails

December 20-December 26, 2008 Edition

The biggest change in Rails in recent memory isn’t reflected in edge Rails yet: I’m speaking, of course, about the merger of Merb into Rails 3 . There is a 3-0-unstable branch in the repository, but it hasn’t yet started to diverge from the main line of development. I’ll continue to focus on the master branch, which will be released as Rails 2.3, for the time being.

And Rails 2.3 is still cooking along. The team managed 39 commits this week, despite people taking holiday time off. Many of those were minor bug fixes, but here are a few things you might want to track in the new development.

Unified rendering

ActionController::Base#render is a lot smarter about deciding what to render. You can just throw things at it and expect to get the right results. If you’re using Rails 2.2, you often need to supply explicit information to render:


render :file => '/tmp/random_file.erb'
render :template => 'other_controller/action'
render :action => 'show'

Now in Rails 2.3, you can just supply what you want to render:


render '/tmp/random_file.erb'
render 'other_controller/action'
render 'show'
render :show

Rails chooses between file, template, and action depending on whether there is a leading slash, an embedded slash, or no slash at all in what’s to be rendered. Note that you can also use a symbol instead of a string when rendering an action. Other rendering styles (:inline, :text, :update, :nothing, :json, :xml, :js) still require an explicit option.

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ActiveRecord fixes

A couple of fixes to ActiveRecord get rid of failing cases for associations. One handles quoting table names in some has_many :through associations – if the table name contains a SQL keyword, then you can’t use it in such an association in Rails 2.2. commit

The other fix allows you to once again use a hash in conditions for a has_many relationship:


has_many :orders, :conditions => {:status => 'confirmed'}

That worked in Rails 2.1, fails in Rails 2.2, and will now work again in Rails 2.3 (if you’re dealing with this issue in Rails 2.2, you can use a string rather than a hash to specify conditions). commit

Some side effects of calling Model#last (it would change the order for other finders within the same scope) have been removed. commit

Prompts for Date Select Helpers

With this patch, you can supply custom prompts for the various date select helpers (date_select, time_select, and datetime_select), the same way you can with collection select helpers. You can supply a prompt string or a hash of individual prompt strings for the various components. You can also just set :prompt to true to use the custom generic prompt:


select_datetime(DateTime.now, :prompt => true)

select_datetime(DateTime.now, :prompt => "Choose date and time")

select_datetime(DateTime.now, :prompt => 
  {:day => 'Choose day', :month => 'Choose month', 
   :year => 'Choose year', :hour => 'Choose hour', 
   :minute => 'Choose minute'})

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Odds and Ends

The dbconsole script now lets you use an all-numeric password without crashing. commit

You can now use symbols for the :type option of send_file and send_data, like this: send_file("fabulous.png", :type => :png). commit

If you’re using Active Support delegates, the new :allow_nil option lets you return nil instead of raising an exception when the target object is nil. commit

You can now specify a particular timestamp for updated_at timestamps: cust = Customer.create(:name => "ABC Industries", :updated_at => 1.day.ago) commit