Now that I'm starting to use DelayedJob to perform jobs in the future in my Heroku Sinatra app, its important that they happen at the scheduled time. But unless you pay attention, you'll find that times get mysteriously changed -- in my case, since I'm in San Francisco in the wintertime, by +/-8 hours -- which means that some conversion to or from UTC is being attempted, but it's only working halfway.
Trying to keep a handle on which libraries are attempting, and which are failing, to convert times is a losing battle, so I'm trying to do the right thing and save all my times in the database in UTC, and convert them to and from the user's local time as close to the UI as possible. Unfortunately, a variety of gotchas in Ruby and ActiveRecord and PostgreSQL makes this trickier than it should be. Here's a little catalog of my workarounds.
Help
Why is upgrading to Ruby 1.8.7 so painful?
More specifically, a Pivot was wondering why there seem to be so many ways to install Ruby and Rubygems on a Mac. There are a lot of different places where gems end up being installed depending on which version of Ruby you have installed, and the specifics of how you installed it. The conversation turned into one about RVM and Yehuda Katz' Bundler, two technologies that appear destined to make it much easier to easily combine a version of Ruby with a set of gems under a particular project.
What is that technology that allows for more complex condition hashes in ActiveRecord?
This must be ActiveRecord::Extensions, which allows for an expanded syntax in the conditions hash of AR finders. A debate was had as to whether hashes and arrays could possibly comprise a reasonable DSL for complex query logic, but surprisingly, the final word on the subject was not reached during standup.
We are using
curlto talk to a Mongrel/Rack server that is running some specs. That server is emitting dots (just as any Rspec process would), but we cannot get those dots to show up in real-time on the client. The only way we've been able to force a flush is with a newline character, but that gives us an ugly vertical column of dots. Any suggested hacks for this?
The Bay Area Chef Meetup Group is meeting on 10/14 in Mountain View. If you're into Chef (and here at Pivotal we use it extensively), you might want to check it out.
Nested attribute assignment is one of the recent additions to Rails that made a great deal of sense, and made a lot of people happy. Chances are you've either used nested attribute assignment by now, or you worked on an older project that really could have used it. If you haven't yet, check it out and see what you think.
Unfortunately, not all is well in Railstown. Nested attribute assignment is slick, and the related implementation of #fields_for makes it even slicker, but #fields_for can cause you some headaches if you're not careful. Possibly if you are careful as well.
One of my favorite computer games when I was growing up was Robot Odyssey; I imagine it will come as a surprise to no one that I was a nerdy kid. This article is a little bit of a tribute to that game, and the coolness of solving complex problems with a handful of simple concepts combined in clever ways.
Imagine you want to write a web-based game that involves robots. The robots in your game are a bit like the robots in Robot Odyssey: you program them with a list of simple instructions and when you turn them on they follow those instructions faithfully. Let's say, for the sake of argument, that your robots can Walk Forward, Turn Left, Turn Right, Jump, and Beep.
Ask for Help
"Has anyone implemented mutli-table (class table) inheritance in Rails, as apposed to single table inheritance (STI)?"
- There are some plugins that nobody has tried, such as inherits_from
- What about a view to represent the super set of tables and rows?
"We're looking for a dead-simple, drop-in JS rating or 'starting' plugin."
Check out the start-rating jQuery plugin. Any other suggestions?
The following monkey patch gives a bit more information in the ActiveRecord SQL logs. Instead of just saying "User Load" it also says the file and line number in your code that asked AR to perform the operation. That way you can have a hope of tracking it down and optimizing it away if at all possible.
User Load (0.2ms) views/main_page.rb:107:in `filters_box' SELECT * FROM `users`
Code after the jump. I guess you put it in environment.rb with all the other monkeys.
A while back I made the point that the HasOneThroughAssociation class in Rails shouldn't be a subclass of HasManyThroughAssociation. I also submitted a Rails patch in which I changed the superclass of HasOneThroughAssociation from HasManyThroughAssociation to HasOneAssociation and moved the shared Through functionality into a module. Despite support from the teeming millions, Rails core team member Pratik rejected the patch for being "just a refactoring."
At Pivotal, we are passionate about test driven development, keeping things DRY, and writing readable and understandable code. Satisfying all of these desires can be challenging, especially when writing test code. In particular, ActiveRecord extensions present several challenges: which models using an extension should we test? How do we both test our extension in isolation while also testing all model's usage of that extension? Is it even worth it?
The answer is yes, it is worth it, and it's also fairly easy, readable, understandable, and DRY. I will present both a common problem and a solution, using a cumulation of technologies and techniques from multiple Pivotal projects, in particular using acts_as_fu to create laser-targeted, isolated, and disposable ActiveRecord models for testing extensions and RSpec shared behaviors to minimize the amount of duplicated test code.
Interesting Things
application.rb vs. application_controller.rb: As we all know,
ApplicationControllerbreaks with Rails convention and lives in theapplication.rbfile, notapplication_controller.rb.Be careful if you create anapplication_controller.rbfile of your own, as this can confuse Rails class loading and might result in Rails deciding not to loadapplication.rb.Google Webmaster Tools: Note that if you are using Google Webmaster Tools that statistics are different for www.example.com and example.com (sans www).
Nested Model Forms are coming in Rails 2.3! There is even a patch in progress.
How many times has this happened to you? You get a cool design for your website, and you spend a bunch of time lining up all of your images and roundy-corner widgets and input boxes just... so..., and everything looks great. But, then you submit a form without typing in your favorite ice cream (a required field, of course), and suddenly your layout is splattered about like an extra large scoop of rocky road in the hands of a two year old. It's enough to make you want to stab your eyes out with a hedge trimmer.