It's the first Wednesday of the month again, and that means it's time for the Pivotal Labs/Outside.In monthly Ruby Happy Hour. It's the first one since GoRuCo, so there's even more to talk about than usual. (Thanks Josh, Francis, and everyone else who made this a great conference again this year.)
Where: Outside.in, 20 Jay St Suite 1019 (10th Fl), Brooklyn, NY
When: 7-9PM today, Wednesday June 3rd
Who: If you’re a developer who uses Ruby and would like to meet some other Ruby folks, toss around ideas, or just have a few beers, we welcome you with open arms!
There will be pizza, beer, and great discussions for everyone. More details on the Outside.In Blog, and please RSVP if you can, so we know how much pizza to get.
Yehuda's GoRuCo talk was on the subject of Rails as a Ruby citizen - that while Rails was already a pretty good Ruby Citizen with 2.3, 3.0 is about making it a better citizen.
Ben Stein of Mobile Commons is giving a talk on Cross-platform Mobile App development. They hadn't done any client mobile work, but lately clients have been asking "what about iPhone?," "what about Android?" and the like. Whether or not this question of navigating the mobile client world is important to you now, Ben predicts it will soon be, as that's where we're headed.
Thoughts and experiences from Mobile Commons' first mobile client apps:
Sandi Metz, a Dukie visiting from NC, will be talking about SOLID principles of software development:
- Single Responsibility
- Open Closed
- Liskov Substitution
- Interface Segregation
- Dependency Inversion
All of Sandi's code is available here.
Change
Fact: your application is going to change. How will your application handle that change?
Robert Martin says your app can behave a couple of different ways:
- Rigid: Making a change somewhere will break something somewhere else.
- Fragile: You can't predict where that break will be.
- Immobile: It's hard to change your code.
- Viscous: It's easier to do the wrong thing than to fix things.
In the beginning, though, your app was perfect. "Dependencies are killing you!"
Design might save you.
The Design Stamina Hypothesis says that, after a certain point, you'll have done better if you had designed first.
"Skip design, if you want your app to fail."
To avoid dependencies, your design should be:
- Loosely coupled
- Highly cohesive
- Easily composable
- Context independent
Ignorable Rules
SOLID principles we can ignore in ruby:
Interface Segregation
Really only a problem for statically-typed, compiled languages. Because we're in Ruby, we don't have this problem! Win!
"Dynamic languages obey this rule in the most extreme way possible: duck typing."
Liskov Substitution
When you design, don't break the contract of the superclass in the subclass.
Testing Interlude
Sandi draws her examples of applicatoin change from the source code at: http://skmetz.home.mindspring.com/img28.html.
Lesson #1: Resistance is a Resource.
- Don't be attached to your first idea
- Embrace the friction
- Fix the problem
If testing seems hard, examine your design. Tests depend upon the design of the code. "TDD will punish you if you don't understand design."
During refactoring, ask yourself:
- Is it DRY?
- Does it have one responsibility?
- Does everything in it change at the same time?
- Does it depend on things that change less often than it does?
The answers should all be 'yes'.
Important Rules
Sandi references her code to demonstrate when and how to mock and use dependency injection to achieve Single Responsibility, in which a class both downloads and acts upon the downloaded data.
She urges developers to do the simplest possible refactoring when extracting responsibilities from a class.
"Refactor, not because you know the abstraction, but because you want to find it."
Sandi uses a very interesting example of building a Config class which behaves differently in different Rails environments. The first version had a lot of smell, and with a combination of hash parameters, YAML file, and metaprogamming, she demonstrates how to be open for extension, but closed for modification.
Sandi explains that paying attention to your classes' dependencies is important. If a relatively static class is dependent on a class that changes more often, that's a smell! Use dependency injection to avoid Dependency Inversion.
Summary
"TDD, BDD and DRY are all good, but they are not enough."
"Design because you expect your app to succeed, and the future to come."
Sandi recommends reading:
Jake Howerton gave a GoRuCo talk about Rails Anti-Patterns, drawn from his years as a rails developer.
Over lunch with Jake, I'd wondered aloud "where are all the wide-eyed optimistic presentations?" and Jake starts by saying he's sorry that this will not be one of those talks.
We've been programming in Rails for several years now, and now more than ever we're left with the problem of how to deal with, maintain and correct projects which may be riddled with out-dated thinking, mistaken ideas and problematic implementations.
In other skilled enterprises there are core ideas which are repeated by for practice and for their general utility. In martial arts, these are called "katas," in programming, we have "patterns." Patterns are general, reusable solutions to common problems in software engineering, which are often arrived at through emergent design. Anti-patterns, likewise, emerge in the general work on a project, but their presence is harmful. They're the mistakes we make again and again in our projects.
Jake then laid out a few patterns and anti-patterns for your consideration:
Dan Yoder is the Director of Development at ATTi R&D, and will be talking about Waves, a Ruby architectural framework for developing RESTful apps.
A Brief History
Ruby web development came of age with MVC and Rails. Later, people who didn't need a full MVC invented Sinatra and other frameworkes. Which brings us to today, and ...
Waves Introduction
Waves can do simple apps in just a few lines of code. And by using "foundations", developers can build more advanced apps with MVC-like functionality. You can build your own foundation for whatever web framework you envision (there are several for MVC and REST).
Waves supports rack::cache and JRuby. It's Actually In Production(tm)!
Web as Services
As more rich browser apps use AJAX and COMET, server-side APIs are becoming more important. This is where REST shines.
"HTTP isn't MVC, but our frameworks think in MVC."
REST and ROA
"REST" shouldn't be applied to things that are "REST-influenced" (just ask Roy). Dan likes to use "Resource-Oriented" for these situations.
HTTP-based ROA uses the existing infrastructure, and has proven scalability. HTTP defines a protocol for a distributed hash table:
- put(key, value)
- get(key)
- delete(key)
Q: "What about post?" A: "Post is for 'everything else'." Some things aren't clearly RESTful, and post is the catch-all for other operations.
What's in the hash? Resources, and keys are the URIs.
What's the point? Platform-neutral distributed objects! RDF can be used to describe discoverable resources.
ROA in action: rss/atom. It's one link to a resource describing your blog. "Boom! Podcasts for free." Dan describes this as the law of "unintended consequences," in a good way.
Edge caching is another big win for HTTP-based ROA.
How Does Waves Help?
Waves makes it easier to write resourceful applications like this today. New foundations will make it even easier going forward.
You can check out Waves at http://rubywaves.com, and on their Google Group.
Eleanor McHugh, a physicist by training, will be talking about how to make *nix systems work naturally within the Ruby environment.
The Unix Way
Eleanor actually hates Unix, but recognizes that it's a very effective operating system for getting things done. It's DRY: build little things, build them well, don't build them twice. There's a natural marriage between agile Ruby and the Unix philosophy.
Unix provides basic services which make it a very useful OS to "muck about with":
- virtual memory
- process management
- hierarchical file system
- user permissions
- interprocess communication
Ruby provides some "really lovely" utilities:
- Kernel.system
- Kernel.spawn
- IO.popen
- Open3.popen3
However, if you're doing a lot of IO, you end up doing a lot of select()s and keeping a lot of file descriptors open.
System Calls with Ruby DL
DL, which Ruby delivers out of the box, is a way to wrap a C library with a Ruby call. This is a nice way to access the underlying kernel system calls without relying on the Ruby IO implementations.
This is superior to Ruby's syscall, in that you can actually get results back from the function call.
Using mmap allows you to do much faster memory reads, rather than do slower file reads.
Using kqueue/epoll/inotify allows you to build evented ruby (like EventMachine, but without EventMachine).
Using pipes allows you to build efficient IPC.
The drawback is that using DL means more verbose code, and more error prone code. (Pointer math FTL!) So, for things like sockets, use the Ruby API unless you specifically need kernel-level eventing.
Multicore
The lack of real thread support in Ruby can be addressed by using multiple processes, held together with IPC (sockets, pipes, memory mapped files). This is the traditional "Unix way" for handling multiple processes.
Gregory Brown is the creator of Ruport and Prawn, and the author of the upcoming Ruby Best Practices. He'll be talking about the various-and-sundry Ruby implementations.
Moving to 1.9
On Ruby 1.8, strings are sequences of bytes. On Ruby 1.9, strings are proper characters (not bytes!). Even if your app only speaks "American", you still need to be aware of this to handle data properly. Plus, some of the new syntax in 1.9 is not backwards compatible with 1.8.
Recommended steps for upgrading from 1.8 to 1.9:
- make sure you have good test coverage!
- make sure your test are checking the output (some end-result validation)
- run on 1.9
- hammer on your code until the tests pass
- decide whether to continue to support 1.8
Prawn only officially supports 1.8.6 and 1.9.1 to make life easier, but if support more versions is necessary for your project, check out ZenTest's multiruby features.
Greg recommends using conditional-execution blocks to make version-dependent code look nicer:
if RUBY_VERSION < "1.9"
def ruby18
yield
end
else
def ruby18
end
end
Greg opines that moving to Ruby 1.9 is not a magic bullet, but has lots of advantages, so try it out!
Ruby 1.8.7
Ruby 1.8.6 is a workhorse (insert image of beat-up pickup truck). Ruby 1.9 is a Lamborghini (we think). "What the hell is 1.8.7?"
Answer: 1.8.7's patch set is largely 1.9 backports. It's a platypus!
However, this doesn't mean that code written for 1.9 will magically work on 1.8.7. Or that code written for 1.8.7 will work on 1.8.6.
What should authors be doing? Should we release for 1.8.6 or 1.8.7? Greg recommends releasing for 1.9, especially if you're writing a Ruby book (wink wink).
Peanut Gallery
Eric Hodel (maintainer of Rubygems), is planning on dropping 1.8.6 support within the next year, but continuing support for 1.8.7 and 1.9.
Writing Extensions
FFI (Foreign Function Interface) is supported "all over the place", and is an alternative to writing a C extension. FFI works across implementations (JRuby, Rubinius, and MRI).
On Windows, Greg proclaims that JRuby is the easiest way to wrap a C library. "WTF?"
Oversimplified Explanations of Ruby Variations
According to Greg. (Not all of the nuance may be captured here, since Greg was moving pretty quickly. Blame me, not him.)
- 1.8.6 is ubiquitous, and may be slowing adoption of other, better interpreters.
- YARV (1.9) is faster than Matz's implementation and is the only complete m17n implementation of Ruby.
- Ruby Enterprise has a great installer!
- JRuby is great and new, but requires C extensions to be rewritten
- Rubinius is what created the RubySpec project and FFI, and is very innovative.
- MacRuby is, um, Ruby for Macs.
Good morning! Today Ben Woosley and I will be live-blogging what's going on during Goruco at Pace University.
You can check out some photos of the conference.
We have a winner in the Pivotal Tracker GoRuCo Haiku Contest.
Collin Miller submitted the winning entry:
Rivers of Action
Clearly Sculpt a Way Forward
My Path is Now Clear
We thank everyone for participating. There were a number of great entries, but this piece really stood out.
Collin, come on down tomorrow and say hi. I'll be there all day enjoying the conference with some other folks from Pivotal Labs and demoing Pivotal Tracker for anyone who doesn't know it already. Congratulations on your win!