Saturday, December 13, 2008

merb and sequel

Recently I needed to order some records by a mathematical formula, and I couldn't figure out a way to do it in DM (although it looks like the idea was well received and might make it into a future relase). I'd heard some great things about Sequel, so I decided to take a look and see what possibilities I had there.

If you haven't read anything about Sequel, head on over to its rubyforge page at There's a good amount of information from basics to how you can implement complex associations between models. There's even a link to Lori Holden's MerbCamp presentation.

Sequel piqued my interest in many ways: it uses the Active Record Pattern to create methods from column names, but you can also do a more DataMapper style definition of columns inside your model:

You can use Post.create_table! as a sort of automigrate (it will drop and recreate the table). The usage of set_schema is more for test code and experimenting, and I found it very useful when developing sequel_polymorphic and sequel_taggable.

So, while its easy enough to generate a new merb core app and customize it as you like, if you're going to be generating a lot of apps with the same configurations, its worth learning how to build a stack. Currently its mostly a manual process: you build a gem with a certain structure by hand, and then use your stack with merb-gen. Eventually this will probably be an easily streamlined process, but for now its still up to you to put things together. You can read more about the structure here and take a look at merb-sequel-stack as well.

If you're looking to get a bit closer to your DB and want a lot of flexibility and power, you should really take Sequel for a test drive. Its current maintainer, Jeremy Evans, has been a ton of help with answering dozens of questions in #sequel, even when its to answer something he doesn't agree with like polymorphic associations, which I'll go into next time.

Monday, December 1, 2008

a possible addition to

The same questions get answered many times a day in #merb and I have to think there's a better way, especially for dependency issues. Whether is a rubygems issue, one with Merb or any of the typical libraries people use it with, or just some random little bug you only see on windows, I haven't seen a good way to track and relate all of this information. Some goes on a wiki, some is remembered and routinely typed back by various people in #merb, some goes to the mailing list. It shouldn't have to be this way, and I'm hoping this idea will help:

dependency hell mitigator

The implementation would be dead simple, probably something like a tag cloud. It'd rely on people entering info and trying to keep things up to date...but hopefully this would result in a more organized and useful collection of all the various tricks we employ to get through those moments of keyboard tossing and mice bashing.

As usual anyone interested in coding this up is more than welcome to--the source is at jackdempsey/builtbythenet If enough people like this idea then I'll probably start in on it myself at some point and see where it goes.

Monday, November 24, 2008

great article on merb-auth

angryamoeba has written up a nice explanation and tutorial of merb-auth over at his blog. If you've been curious about how the pieces fit together, or just want to get merb-auth up and running, take a moment and head over.

Friday, November 14, 2008

I launched a site today

It takes a number and divides it by 86,400. The next iteration will include functionality to take a number and multiply by 86,400. Amazing right?

The site has no design. I don't have a business plan. I don't have sales, marketing, QA, or anyone else. And I couldn't care less.

I realized today that I agree with "release early, release often", that I try to live by those words when I can, but as a developer you only have so much control over what your boss thinks, plans, schedules, and so on. At night you're perfectly free to release any sort of crap you want, when you want to, and similar to my recent post on testing, I've realized I need to just get over my desire to perfect things and refactor ad infinitum, and just ship something.

So the site is simple. It basically does nothing right now but convert the number of requests per day into what it'd be in requests per second. This came out of a discussion with Topfunky who was wondering what 8 million requests a day would be in RPS. It was a perfect example feature to spawn the launch of

The idea is simple--GitHub brings you "Social Code Hosting" right? Well, think of this as Social Site Building. Users can submit feature requests at, vote for other's ideas, and take part in building a site like never before, because not only do the users drive development, the code is completely open:

People often say "I'd love to learn Merb, but am tired of building blogs. What should I build?" Well, now you have something else to try out. I imagine, at least I hope, that over time some great ideas will come out of the ether. The possibilities are endless. The 'goal' in my mind is less about what the end result is, and more about the process and the features along the way. I don't think this will ever be finished. Maybe in a few weeks it'll fall flat on its face and oh no, I'm out a $9.95 domain name. But at least I'll have tried...and if all that comes of this is another example of some Merb code, that's good enough for me.

Wednesday, November 12, 2008

rspec macro methods in Merb

While working on spec'ing out this merb-service-example app I came to a point where I had a lot of repetitive code, enough that I really wanted to DRY it up a bit. Long story short, after talking with David Chelimsky for a bit, I ended up with this: gists_spec.rb

I think the it_should_respond_with and it_should_return methods work well for adding clarity, reducing repetition, and making the specs even stronger. Still, I'm a bit unhappy with the method names. Some other possibilities thrown out there are:

Nothing feels perfect yet...and maybe it doesn't need to be...but, that's never stopped me from trying. What name(s) do you like? Any better suggestions?

Get over yourself and write that test

I've had to tell myself this a bit recently...and it wasn't the medium you'd expect.

I'd been working on a particularly tricky Sudoku know the kind where you've got lots of squares completely solved, and yet some are mostly blank? No matter what I did, I couldn't find a damn 7,8, or 9 to set off a finishing chain of selections. I also have this stubbornness that forces me to try and solve the hard puzzles without using notes. I almost always can, and yet this particular puzzle was besting me.

Its ok, I just have to try harder, right? Focus more, go over the various possibilities, what could this being here mean, and so on. Another 20 minutes pass and no progress. With a sigh I finally gave up, and started sketching out all of the possibilities. Within 3 seconds of doing so, I saw an obvious selection I had missed. This set off another, and another. 2 minutes later I was done.

Part of me felt like I "cheated"--any great Sudoku solver wouldn't need such help, right? At the same time, there's a point where the challenge of solving the puzzle degrades into frustration and really a waste of my time, and in this case I had long overshot that mark.

Feel familiar yet?

I couldn't help smiling as I thought about this on the metro in this morning. It reminded me of every time I'd sit down to write some code, get it wrong, redo some things, get it right...and then find out I really didn't...and repeat this process until I'd finally write a few tests and voila, be done with it.

I remember back in college hearing these epic stories of masters who could code in C, top to bottom, and at the end magically compile things without error. I think of people I know who can jump into a presentation, test, interview, or module, and just get what they need done without a moment's hesitation or need of 'backup' or notes.

I used to be one of those people...but I think lots of us were, back in 5th grade, just excited to learn the next set of formulas or geometric equations. I'm not anymore, and I'm ok with that. There's a certain peace of mind, a certain relaxation I feel, when I have code that's spec'ed, tested, and banged on to the point where I own it, and not the reverse.

Something I think people don't say enough, even with the tons of discussions about tests: even if your tests suck, even if they mock too much, are too brittle, and perhaps miss some important cases, the knowledge of the code that you receive while writing those tests is extremely valuable. The investment in your own ability to write those tests is extremely valuable. Testing really is like working out, and I've slipped as of late (in both areas), and can feel it.

I made the decision recently to change both of these things, and just like getting back into the gym has given me more energy and I just feel better, getting back into writing some tests has reminded me just why we should do it in the first place.

I've been flexing this rebirth with a simple merb 1.0 service example app located at and you'll see its using the new request helper. I'd talk more about that, but wycats has done so already, so I'll just say: you really, really want to test this way as opposed to mocking everything out. It allows for a very fluid and flexible inner workings of your controller, while verifying things come back as they should.

PS: I even TDD'ed this post via a friend checking it. As you'd expect, I was shown several 'bugs' and issues. Thanks again Doug

Tuesday, November 11, 2008

Installing Merb 1.0 on Debian

This has come up a few times in #merb: as a result of the webrat and nokogiri dependencies, if you're looking to install 1.0 on a Debian box, make sure you have the following packages installed:

libxml-ruby libxslt-ruby libxml2 libxslt1-dev

Thanks to mr-interweb and maxbaroi for some late night detective work. The relevant ticket is located at

Wednesday, November 5, 2008


Recently I've been looking over my various github projects, and am trying to give some love to things I haven't touched in a while. First up: acts_as_commentable.

A small amount of history first: the plugin was originally developed at

There've been many comments on it since then. My original intention was to port it over to something we could use in Merb. Turns out that actually didn't require much...actually, it was basically just an extra require in the library. I've touched things up a bit and have updated the repo at

I've sent an email to the original author as I'm not trying to pirate his/her stuff...we'll see what comes of that, but I noticed the other day that there were 54 or so watchers (and on a tangent--I mentioned that in #github and this might have sparked some ideas along the line of being able to easily see who's watching your repos), so hopefully those who're interested can play with things, and finally have a vehicle to contribute if desired.

Please feel free to send me comments, patches, etc. Something this widely used is just being for community support and feedback.

Sunday, November 2, 2008

useful snippets

I rely on a number of aliases, shell scripts, and whatever time savers I can come up with. You never know what you might learn by seeing someone elses, so here's a few of my favorites:

I've mentioned the cdargs stuff before, and there's a great post talking about git bash completionfor those interested.

k, now it's your turn.

Monday, October 20, 2008

Creating a new Merb stack with Templater

In trying to remove Merb's dependency on ActiveSupport, Jonas Nicklas developed Templater. I'm going to show you briefly how to use it to create an ActiveRecord, TestUnit, and Prototype based Merb stack.

I'd like to make clear at this point that this is more for learning about Merb, generators, and to use as a reference point for creating other stacks. I prefer DataMapper, Rspec, and JQuery, and as such this example stack won't be supported officially or unofficially (unless someone else would like to...if so, let me know).

You can find the code here:

The first important piece is the Generators file:

scope 'merb-gen' do
dir = File.join(File.dirname(__FILE__), 'lib', 'generators/')
Merb.add_generators dir + 'merb_ar_stack'

This file is picked up by Templater and as such, when merb-gen is run, you'll see it listed as one of the available generators. Lets take a look at what merb_ar_stack actually is then.


module Merb
module Generators
class MerbArStackGenerator < AppGenerator
# ==== Paths

def self.source_root
File.join(super, 'application', 'merb_ar_stack')

def self.common_templates_dir
File.expand_path(File.join(File.dirname(__FILE__), 'templates', 'application', 'common'))

def destination_root
File.join(@destination_root, base_name)

def common_templates_dir

def testing_framework

def orm

# ==== Generator options

option :template_engine, :default => :erb,
:desc => 'Template engine to prefer for this application (one of: erb, haml).'

desc <<-DESC
This generates a "prepackaged" (or "opinionated") Merb application that uses ActiveRecord,
TestUnit, helpers, assets, mailer, caching, slices and merb-auth all out of the box.

first_argument :name, :required => true, :desc => "Application name"

# ==== Common directories & files

empty_directory :gems, 'gems'
file :thorfile do |file|
file.source = File.join(common_templates_dir, "merb.thor")
file.destination = "tasks/merb.thor"

template :rakefile do |template|
template.source = File.join(common_templates_dir, "Rakefile")
template.destination = "Rakefile"

file :gitignore do |file|
file.source = File.join(common_templates_dir, 'dotgitignore')
file.destination = ".gitignore"

file :htaccess do |file|
file.source = File.join(common_templates_dir, 'dothtaccess')
file.destination = 'public/.htaccess'

file :doctask do |file|
file.source = File.join(common_templates_dir, 'doc.thor')
file.destination = 'tasks/doc.thor'

file :prototype do |file|
file.source = File.join(common_templates_dir, 'prototype.js')
file.destination = 'public/javascripts/prototype.js'

directory :test_dir do |directory|
dir = testing_framework == :rspec ? "spec" : "test"

directory.source = File.join(source_root, dir)
directory.destination = dir

# ==== Layout specific things

# empty array means all files are considered to be just
# files, not templates
glob! "app"
glob! "autotest"
glob! "config"
glob! "doc", []
glob! "public"
glob! "lib"
glob! "merb"

invoke :layout do |generator|, options, 'application')

add 'ar-app', MerbArStackGenerator

Pretty straightforward, right? You'll see a couple places easily configured to be whatever you like, as well as listing of various files you want to include (like the prototype.js reference).

Beyond that, you'll see inside lib/generators/templates an application directory that holds a directory for the common files you'll use as well as a directory that actually lays out what the generated app will look like.

The final important piece is inside the Rakefile:

gems = [
["merb-core", "~> #{GEM_VERSION}"],
["merb-more", "~> #{GEM_VERSION}"],
["activerecord", "~> 2.1.0"]

This array is used later in the rake file by add_dependency. It takes care of bringing in the various gems needed for your stack. Take a look here to see what the official stack depends upon.

Thats pretty much it. There are other pieces that you'll want to configure things (like in the config/init.rb file inside your templates/application/merb_ar_stack folder for instance). I'd recommend forking this repo and tinkering with things a bit to get a feel for how it all fits together.

Things have been a bit busy recently, so I haven't had as much time for blogging as I'd like. I hope to write more in the near future when 1.0 is out and people are looked to really dig into things.

Tuesday, September 9, 2008

Thor finds Mjolnir

If you've been following the development of Thor, you'll know there's been a bug that affected commands with several layers of namespacing. Tonight I'm happy to announce this bug was finally crushed by Yehuda Katz.

Just to briefly describe the pain this has brought me, a few facts:

* Class.constants only gets the top level constants. If you have Foo::Bar::Baz, don't expect to see Baz in Foo.constants

* Struct is mean:

(You can imagine how the first point led me to the second, right?

* Remember, when you ask for constants on a class, it:

Returns an array of the names of the constants accessible in mod. This includes the names of constants in any included modules (example at start of section).

It _also_ returns constants defined in any class you inherit from.

So, lets just say this all added up to a nice bit of hacking for me, and truthfully it was a good experience. It started to get old after a while, but I think this is something people don't talk about enough. Its the same with lifting weights: you purposely destroy and rip apart your muscles so they can build up bigger and stronger next time.

If you don't at least semi-often tackle hard problems, frustrating situations, and just fight through those moments when you think "screw it, PHP isn't that bad", you'll never get the kind of experience that really makes you grow as a Rubyist, and really, a programmer. You'll often find at the end not only did you learn some new tricks, but sometimes the solution is right there before your eyes....or Yehuda's eyes...but still, you'll get a lot out of it.

So anyway, I'm happy to point people to and say 'Enjoy!' The soon to come Merb bundling tasks will be taking advantage of Thor's power, so if you haven't done anything with Thor yet, now's a great time to jump on board.

Saturday, September 6, 2008

router redirects

Merb's router supports a nice redirect feature:


One item of note--this redirect defaults to a 301 status, so if you're playing around with this and want 302's instead, pass a false as a second parameter to redirect:

r.match('/').redirect("/login", false)

If you happen to confuse this and set a permanent 301, just add in the false, hit the page again, let the 302 be processed, and you should be good after taking out the redirect again.

Thursday, September 4, 2008

A script to help with Rails -> Merb conversions

People have asked often in #merb for something to help with converting Rails apps to Merb apps. There's no magic Wizard to do this for you, but hopefully this will help:

Its a standalone Thor script that looks in your current directory (or a provided path to an app), finds the app/ directory, and scans through the code for a variety of things that people get tripped up on in Merb. I imagine this list will increase over time, but it will help with some of the obvious ones to start.

This is very much a work in progress. Running it standalone like this, especially given the way I've organized it, loses some of the flexibility Thor provides. It also makes it easier on the user to invoke. I imagine if this is used by people and grows to be anything bigger than a simple helper script, I'll refactor the way the task is started, so I'd recommend cloning this and playing with the source a bit as well.

Anyway, if you haven't played with Thor yet, you should give it a go. Its fast, flexible, and a great way to avoid the "fun" of parsing options yourself.

Currently there's a bit of an issue with installing tasks that have multilevel namespaces. For the time being, I've committed a fix to the constants branch of my fork at

I foresee this fix getting cleaned up and merged into the main Thor repo soon. In the meantime, if you're looking at using Thor with tasks like foo:bar:baz, this fork will fix things up for you.


I fixed things up a bit so that we can search on regex's as well. This came out of a discussion in #merb re: the tendency to "redirect && return" in Rails, which is the reverse of what you'll want to do in Merb.

Saturday, August 30, 2008

Experimenting with Ubiquity

For those of you who know what Ubiquity is, I'll keep this brief. For the non-initiated, take a second to read about what many describe as Quicksilver for Firefox:

You can install it here, read the tutorial and then come back when up to speed.

Cool stuff, right? So I took a look at their wiki earlier and was kind of surprised to find that nothing was listed there for Ruby...but you could search for php functions? I took their code and hacked it up a bit:

Easiest way to play with this in my opinion is, once you've installed Ubiquity, test it at chrome://ubiquity/content/editor.html

As you can see from the gist, its pretty easy to create a new command to play with and you can easily add in search capability for your favorite site. If its well known there's a shot someone's done that already.

Anyway, I thought this was pretty cool and imagine over time it will enable some pretty interesting mashups. Its almost a more powerful and approachable version of Yahoo Pipes, albeit a different sort of beast.

As I get time I'll be playing more with it, probably hooking up some nice Merb search capabilities. Feel free to drop some comments if you have some ideas, but perhaps aren't familiar with Javascript or coding in general. Enjoy!

Monday, August 18, 2008

Updated merb-thor tasks

Lots of questions have come up regarding sake in #merb recently. The current sake tasks at are out of date, so I updated the tasks inside merb-more itself. You can install using:

For those interested in Thor, I've also updated the tasks at:

They, like the sake tasks, are particular about directory structure, so make sure you've set things up, and run things from the correct directory.

Wednesday, August 6, 2008

A Mac zoom key

I'm a bit picky when it comes to how I interact with my system; I have tons of aliases, shortcuts, quicksilver triggers, pretty much anything that will save me typing. One that I use every day is a trigger for Zoom.

Open up System Preferences and click on Keyboard & Mouse. Select the Keyboard Shortcuts tab, and click on the plus at the left to add a new one. You'll want to type in Zoom and whatever key combo you wish--I like shift-cmd-M.

Should look something like this:

Save that and open a new terminal window and give it a go. It will of course work in whatever app you can zoom in, I just find I use it in terminal and sometimes my browser almost all the time.


Monday, August 4, 2008

merb-dev sake tasks update

People mentioned today that the sake tasks were broken, so as of commit 123f1e13e96ba6d42cbb0d25554913ab9851cd6a in merb-more you should be good. I changed the installation of primarily the extlib library, and reordered things a bit. As Yehuda mentioned recently, when living on the edge things can be a bit unstable. The pain this may create now is a small price to pay for a 1.0 release thats solid and easily used by many, so please stay tuned and keep the comments coming in #merb.

Sunday, August 3, 2008

a quick note on deploying with git

I've deployed a merb app and rails app recently with git, both on boxes. For one I didn't need this option, and yet for the other I, to anyone having issues with git deployment with capistrano, see if this helps. In your deploy.rb file add this line:

default_run_options[:pty] = true

The guys at mention this in their guide to deploying with capistrano as well, so if you need other clues I suggest checking that out.

Monday, July 14, 2008

leopard, rubygems, and bus errors

Every now and then I catch one of these errors:
~/git/project_foo $ rake -T
(in /Users/jackdempsey/git/project_foo)
/usr/local/lib/ruby/gems/1.8/gems/libxml-ruby- [BUG] Bus Error
ruby 1.8.6 (2007-09-24) [i686-darwin9.0.0]

Abort trap

In my experience this just means that you've done some custom stuff to ruby on your Leopard install, and the bundled gems that come with Leopard these days aren't happy. Simple fix, just uninstall the gem and reinstall. This gives things a chance to build the extensions correctly, and be happy from then on:
~/git/project_foo $ gem list lib

*** LOCAL GEMS ***

libxml-ruby (
~/git/project_foo $ sudo gem uninstall libxml-ruby
Successfully uninstalled libxml-ruby-
~/git/project_foo $ sudo gem install libxml-ruby
Building native extensions. This could take a while...
Successfully installed libxml-ruby-0.7.0
1 gem installed
Installing ri documentation for libxml-ruby-0.7.0...
Installing RDoc documentation for libxml-ruby-0.7.0...
~/git/project_foo $ rake -T

(things show nicely now)

Thursday, July 10, 2008

logging to a file in production merb

This comes up often in #merb. You can use several flags to customize things nicely:

merb -e production -l debug -d

This sets merb to run in the production environment, to use a log level of debug (use merb --help to see the others), and -d to daemonize and not log things to the console window.

introducing merb-thor

About a year ago I was working with an ActiveRecord model, and for some reason things would blow up when I tried to do anything to this model inside rake. Turns out having a field called 'link' was a very bad idea, given the rake code bel
# ###########################################################################
# Include the FileUtils file manipulation functions in the top level module,
# but mark them private so that they don't unintentionally define methods on
# other objects.

include RakeFileUtils


The problem is our friend "send" and the fact that it could care less about the call to private. This cost me the better part of a night, and I guess I've never really forgiven rake for it...

Enter thor. If you haven't heard of this, take a look here and see what you think. The code is practically 100% covered by specs, and is easy to dive into...and something just feels better about defining plain old ruby methods instead of tasks.

So, in the interest of learning thor better, I took the merb sake tasks and converted them to their thor equivalents. The end result is found at and once you have thor installed you should install the file with
$ thor install --as=merb

The --as option lets you name things nicely so in the future you can do

$ thor update merb

to get any new stuff thats added in.

I'm happy to take comments, updates, patches, etc. Enjoy!

There appears to be a small bug with namespacing of commands. For the time being, all of the commands should work if you run them inside a directory where merb.thor exists. I hope to have this fixed over the next few days, but til then, this should be a quick solution.

Update Part Deux
I've created a fork of thor in a branch you can find at:

If you install from here thor will load all .thor files it finds in your root whether they're relevant or not. This will get around the constants issue preventing things like 'thor merb:gems:refresh' from working.

Update Part Finale
So merb-thor has grown up and become part of the merb stack. I've updated the repo to point to the new goodness, but if you're reading this you can go there directly:

Much thanks to those who've shown interest in it, sent me patches, etc, I appreciate it. I'll be working on new and exciting stuff with Thor in the future, and if you have thoughts/ideas on things like let me know!


I'm a fan of aliases and basically anything else that can help me type less when doing stuff on the command line. My home directory often has a number of symbolic links to various projects and libraries, and 'til now I've gotten by with this amalgamation of tools and techniques just fine.

Still, I'm always looking out for new tips and tricks, and one of the best and easiest ways to pick up some invaluable knowledge from others is to see how they use their shell. I forget sometimes that some of the shortcuts I know and love aren't used by others; I've had people say "wait, what was that?" when I do

$ mkdir something_here
$ cd !$

or even a simple !!, !mer, ctrl+r rake, etc. Still, you can only know so much, and recently I was that person saying "waaaiiit a sec..." while watching wycats fly around various directories with this little command 'cv'.

Enter cdargs

Take a look at its homepage here and come back when done scanning.

If you follow the instructions you'll have a nice and small 'cv' command at your disposal. Now, maybe it was related to the fact that I was doing this at 3am, but I definitely didn't get it at first, and its actually quite simple.

In browse mode you can easily traverse your file system and type 'a' along the way to add directories to your list. This means that you can just type 'cv' from anywhere, easily select something from your list, and change to it quickly. Nice, but still a little verbose for my liking. However, you can also use a name from your list and cv to it directly, which is just damn cool.

So, an example. My current list looks something like this:

0 [merb ] /Users/jackdempsey/git/merb
1 [thor ] /Users/jackdempsey/git/thor
2 [dm ] /Users/jackdempsey/git/dm
3 [git ] /Users/jackdempsey/git
4 [recollectr] !/Users/jackdempsey/recollectr
6 [testbed ] /Users/jackdempsey/testbed

Which means from any location i can type 'cv git' or 'cv merb' etc and jump to the directory directly. So much nicer than the 'cd ~/symbolic_link_here' that I've gotten used to.

So try it out. I think its one of those things that as soon as you build up the muscle memory for it, you'll never want to go back. Much thanks to Yehuda for showing me the light on this one.

Saturday, July 5, 2008

merb-auth, webrat, and merb_stories

Recently I've been working on getting some stories written for and given that I just added in MerbAuth support, I thought now would be a good time to dive back into the previously paused process.

If you're interested in using webrat for merb_stories, you'll want to get the fork that supports merb from here:

I'd previously had some stories working with webrat and edge merb, but it looked like the upgrade to using MerbAuth in slice form broke some things. After some investigation I realized that the namespacing that's used in merb-slices was slightly different than what the merb supported fork of webrat was happy with...gwynm's fork adds a cookies= method to Application as follows:

class Application < Merb::Controller
def cookies=(newcookies)
@_cookies = newcookies

This is fine except with MerbAuth, we have MerbAuth::Application, and as such things were busted a bit. So, doing the same for MerbAuth::Application fixed things right up:

module MerbAuth
class Application < Merb::Controller
def cookies=(newcookies)
@_cookies = newcookies

Thing is, this doesn't exactly belong in MerbAuth as its specific to webrat....and it doesn't exactly belong in webrat as its going to be an issue to any merb-slice. So for the time being I have this in my app code, and things work nicely. I'll probably write a little more and maybe give some examples for general webrat and merb_stories usage, but til then hope this helps anyone else trying all three of these great components.

Sunday, June 29, 2008

undefined method 'each' for nil

A common error that trips up Rails converts is the fact that you need to manually call 'render' inside your controller actions. If you don't, you'll see something like this:

/usr/local/lib/ruby/gems/1.8/gems/merb-core-0.9.4/lib/merb-core/rack/handler/mongrel.rb:85:in `process': undefined method `each' for nil:NilClass (NoMethodError)

You'll see the code around line 85 is:

if Proc === body
body.each { |part|
response.body << part

As you can see, if nothing is returned from your action, body will be nil, and the each call will fail with the above message.

There's a plugin in the works to help catch some of these issues. In the meantime, I hope this helps!

assets not displaying

A change was made recently to how Merb handles assets, and the result is that users with apps that predate this change will not have their assets displayed. The quickest fix is to delete the config/rack.rb file in your app and let the Merb defaults handle things.

issues with dependency

Some people have reported issues with using dependency to load gems into their environment. The issues are hard to track as it works for some and fails for others. If you do find yourself with gems not loading from a dependency call, you can always use require.

This issue is known and effort will be made to have it resolved by Merb 1.0. Til then, require when needed.

superclass mismatch

A 'superclass mismatch'  is ruby's way of telling you that you're trying to define/open a class who's superclass is different than what its previously recorded. An example:

irb(main):001:0> class Foo; end
=> nil
irb(main):002:0> class Bar; end
=> nil
irb(main):003:0> class Baz < Foo; end
=> nil
irb(main):004:0> class Baz < Bar; end
TypeError: superclass mismatch for class Baz
from (irb):4
from :0

What this usually means is that you're using a name thats already been used, and often you may not realize it. Earlier today someone in #merb had this exact issue when trying to define a class named Region. So, if you see this error popup, you can usually rename your class to something else to make sure the name is unique and that you're not inadvertently reopening a previously defined class.