Dejan Simic

Don't wish it were easier

2011-12-03T00:00:00+01:00

“Don’t wish it were easier; wish you were better. Don’t wish for less problems; wish for more skills. Don’t wish for less challenges; wish for more wisdom.” ~ Jim Rohn

Compiling Ruby on a fresh Lion install

2011-10-25T00:00:00+02:00

During the setup of my development environment on my new iMac, I’ve run into these two issues while trying to install first Ruby (1.8.7-p352) inside rbenv:

Latest XCode 4.2 does not install (non-llvm) gcc-4.2 anymore

I was getting this error:

./configure: line 3211: /usr/bin/gcc-4.2: No such file or directory

Setting the CC environment variable to use /usr/bin/gcc did fixed compiling, but Ruby was throwing segfaults.

The real fix is to install the osx-gcc-installer.

OS X provides the BSD libedit library, which shadows libreadline

I was getting this error:

readline.c: In function ‘username_completion_proc_call’:
readline.c:730: error: ‘username_completion_function’ undeclared (first use in this function)
readline.c:730: error: (Each undeclared identifier is reported only once
readline.c:730: error: for each function it appears in.)
make[1]: *** [readline.o] Error 1

I’ve fixed it by installing readline with brew and configuring Ruby compilation to use it:

$ brew install readline
$ CONFIGURE_OPTS="--with-readline-dir=$(brew --prefix readline)" rbenv install 1.8.7-p352

Inline logging in Rails console

2011-07-17T00:00:00+02:00

While trying out some code in console that deals with storage I find it really useful sometimes to have log output inline (and not in another window that tails the environment log) so I can see right there what’s going on - generated SQL that hits database as well as interaction with the cache store.

Here’s how you can set it up when needed:

# ActiveRecord - Rails 2
ActiveRecord::Base.connection.instance_variable_set :@logger, Logger.new(STDOUT)

# ActiveRecord - Rails 3
ActiveRecord::Base.logger = Logger.new(STDOUT)

# Cache Store - Rails 2 & 3
ActiveSupport::Cache::Store.logger = Logger.new(STDOUT)

You can set this to run every time you’re in console by adding this in environment.rb

if "irb" == $0
  ActiveRecord::Base.logger = Logger.new(STDOUT)
  ActiveSupport::Cache::Store.logger = Logger.new(STDOUT)
end

This is how it looks like in my console while I’m developing my upcoming Rails plugin for caching:

>> User.last.cached(:profile)
  User Load (0.000581) (1 Row)   SELECT * FROM `users` ORDER BY users.id DESC LIMIT 1
Cache miss: User[65]#profile
  Profile Load (0.000454) (1 Row)   SELECT * FROM `profiles` WHERE (`profiles`.user_id = 65) LIMIT 1
Cache write (will save 1.64ms): User[65]#profile
=> #<Profile id: 65, first_name: nil, last_name: nil, ...>

Sweet, though I’d prefer if Cache Store would log raw commands to cache store (Redis, MemCache,…) just like ActiveRecord logs SQL.

Kids, don't try this at work

2011-07-09T00:00:00+02:00

A user is experiencing a nasty bug in your webapp in production that you can’t reproduce locally, and you need to fix it super fast. What do you do?

Start the SSH tunnel to your production database

ssh -f killerapp.db.example.com -L 3307:127.0.0.1:3306 -N

3306 is the port MySQL usually runs on. 3307 is the local port we’re opening for the tunnel. We’ll use SSH tunnel so that we don’t have to deal with firewall poking or mysql granting.

Configure your app to use the tunnel as database

Basically you just need to change connection settings to use port:3307 and host:127.0.0.1 and the login/password of course.

Have some haxor backdoor

This will allow you to login as a user without user password. It’s best to make this code work only in development environment in case of the accidental commit - ring any bells? Here’s one example in Rails: http://mislav.uniqpath.com/rails/haxor-backdoor-in-development. Adjust it to work with your system and your use case.

Handle subdomains if any

If your app is using subdomains you should already be using Tim Pope’s smackaho.st which saves you the trouble of messing around with /etc/hosts

Be fucking careful!

Your local code will now work with production data and you’ll be able to login as a user which means you should really be careful about what you do with data.

The opposite

2011-01-26T00:00:00+01:00

Derek Sivers: “In China there are doctors that believe that their job is to keep you healthy. So any month you’re healthy - you pay them, any month you’re sick - you don’t have to pay them, they job is to get you healthy again so they can get paid again. It’s kind of cool that they get rich when you’re healthy, not sick.”

Resolve all errors in Hoptoad for free

2011-01-23T00:00:00+01:00

Apparently one needs a paid account to resolve all errors in Hoptoad. Fortunately there’s an API for the rest of us cheap bastards. Bellow is the Rake task that saves me $5 per month. Note that API doesn’t have bulk-resolve operation as I’ve expected, so time of execution depends directly on the number of unresolved errors.

require 'httparty'

namespace :hoptoad do
  task :resolve_all do
    
    # your credentials
    subdomain = 'killerapp'
    auth_token = 'ca140f0d8076e0f4e09237d0f45c70d0f4fc56e3'

    url = "http://#{subdomain}.hoptoadapp.com/errors.xml?auth_token=#{auth_token}"
    while errors = HTTParty.get(url)['groups'] do
      errors.each do |e|
        HTTParty.put(url.gsub('.xml', "/#{e['id']}"), :headers => {"Content-length" => "0"}, :query => {:group => {:resolved => true}})
      end
    end
  end
end

Release process

2010-11-11T00:00:00+01:00

Kent Beck: “I remember hearing a description of the release process at Microsoft, and someone likened it to jello. You got this software and it’s like jello. And people are making changes and it’s shaking and it’s shaking, and you think you’re getting close but the software is still shaking. And then it stops shaking just for a second and that’s when you ship it!”

espeak-ruby

2010-10-21T00:00:00+02:00

espeak-ruby is a small Ruby API for utilizing espeak and lame to create Text-To-Speech mp3 files.

Demo

Tweak options, enter some text, hit enter and listen!

Example usage

require 'espeak-ruby'

include ESpeak

# Creates hello.mp3 file in working directory
espeak("hello.mp3", :text => "Hello World") 

# Creates /home/espeak/hello-de.mp3 file
espeak("/home/espeak/hello-de.mp3", :text => "Hallo Welt", :voice => "de")

Features

Currently, only subset of espeak features is supported, but the important ones are there:

:voice => 'en',   # use voice file of this name from espeak-data/voices
:pitch => 50,     # pitch adjustment, 0 to 99
:speed => 170     # speed in words per minute, 80 to 370

These are default values, and they can be easily overriden:

espeak("zdravo.mp3", 
  :text => "Zdravo svete", 
  :voice => "sr", :pitch => 90, :speed => 200)

Sinatra example

If you’ve been wondering about the demo above, it’s powered by this simple Text-To-Speech micro webapp in Sinatra:

  %w(rubygems 
     sinatra 
     espeak-ruby
     digest/sha1).each { |l| require l }

  include ESpeak

  get '/tts' do
    filename = "tmp/#{Digest::SHA1.hexdigest(params.to_s)}.mp3"
    espeak(filename, params)
    [200, {'Content-type' => 'audio/mpeg'}, File.read(filename)]
  end

Install

gem install espeak-ruby

In order to use the gem you must have espeak and lame installed. On Ubuntu Linux, it’s easy as:

sudo apt-get install lame espeak

Source

Find it on GitHub: https://github.com/dejan/espeak-ruby

Credits

Author: Dejan Simic

auto_html

2010-08-15T00:00:00+02:00

auto_html is a Rails extension for transforming URLs to appropriate resource (image, link, YouTube, Vimeo video,…). It’s the perfect choice if you don’t want to bother visitors with rich HTML editor or markup code, but you still want to allow them to embed video, images, links and more on your site, purely by pasting URL.

Demo

Example usage

Transforming string with text and URLs is done with auto_html method:

inlcude AutoHtml

auto_html('Hey! Checkout out: http://vukajlija.com') { simple_format; link(:target => 'blank') }
=> "<p>Hey! Checkout out: <a href='http://vukajlija.com' target='blank'>http://vukajlija.com</a></p>"

You’ll probably have user input stored in model, so it’s a good place to automate and even store this conversion for performance reason. This is done with auto_html_for method. Let’s say you have model Comment with attribute body. Create another column in table Comments called body_html (this is optional, but recommended for performance reasons). Now have something like this:

class Comment < ActiveRecord::Base
  auto_html_for :body do
    html_escape
    image
    youtube(:width => 400, :height => 250)
    link :target => "_blank", :rel => "nofollow"
    simple_format
  end
end

… and you’ll have this behaviour:

Comment.create(:body => 'Hey check out this cool video: http://www.youtube.com/watch?v=WdsGihou8J4')  
=> #<Comment id: 123, body: 'Hey check out this cool video: http://www.youtube.com/watch?v=WdsGihou8J4', body_html: '<p>Hey check out this cool video: <iframe class="youtube-player" type="text/html" width="587" height="350" src="http://www.youtube.com/embed/WdsGihou8J4" frameborder="0"> <br /></iframe></p>'>

Note that order of invoking filters is important, ie. you want html_escape as first and link amongst last, so that it doesn’t transform youtube URL to plain link.

Now all you have to do is to display it in template without escaping, since plugin took care of that:

<% for comment in @comments %>
   <li><%= comment.body_html %></li>
<% end %>

If you need to display preview, no problem. Have something like this as action in your controller:

def preview
  comment = Comment.new(params[:comment])
  render :text => comment.body_html
end

Plugin is highly customizable, and you can easily create new filters that will transform user input any way you like. For instance, this is the image filter that comes bundled with plugin:

AutoHtml.add_filter(:image) do |text|
  text.gsub(/http:\/\/.+\.(jpg|jpeg|bmp|gif|png)(\?\S+)?/i) do |match|
    %|<img src="#{match}" alt=""/>|
  end
end

Non-ActiveRecord models

AutoHtml uses standard ActiveModel API, which means that you can include AutoHtmlFor module (that automates transformation of the field) in any non-ActiveRecord model that uses ActiveModel. Here’s working mongoid example:

class Post
  include Mongoid::Document
  include AutoHtmlFor

  field :body

  auto_html_for :body do
    simple_format
    link
  end
end

Rake and Capistrano tasks

AutoHtml has a Rake task for rebuilding cached in DB column values. Usage:

rake auto_html:rebuild CLASS=yourmodel

Where ‘yourmodel’ is the name of model which values you want to rebuild.

If you want to run it on remote server, just add this to your deploy.rb:

require 'auto_html/capistrano'

Now you can run:

cap auto_html:rebuild CLASS=yourmodel

Bundled filters

For filter list and options they support check: http://github.com/dejan/auto_html/tree/master/lib/auto_html/filters

Install

Specify the gem in Gemfile of the project

gem "auto_html"

Source

As everything these days it’s on github: http://github.com/dejan/auto_html

Credits

Author: Dejan Simic
Contributors: Claudio Perez Gamayo, Matt Polito, Ryan Heneise, Caleb Wright, Derrick Camerino, Daniel Weinmann, Edgars Beigarts, Henning Thies, rbq, Kir Shatrov (Evrone Company), Demange Anthony, Hinrik Örn Sigurðsson

Yesterday's Weather

2010-07-03T00:00:00+02:00

Pomodoro Technique Illustrated Book:

A national weather service spent a gigantic amount of money on a new forecast system. All the emerging technology was included, and it had an accuracy rate of almost 70 percent.

Then a clever person challenged the super machine with a much simpler algorithm. It was called Yesterday’s Weather, and it said, “Tomorrow will be like today.” Guess what? It had the same accuracy as the super machine.

Distinct values in Rails

2010-05-23T00:00:00+02:00

First of all don’t do this http://snipplr.com/view/21497/distinct-in-rails. I’m not even linking it since somehow that’s already ranked #5 for “rails distinct” on Google.

One way is to use :select option in ActiveRecord finder.

>> User.all(:select => 'distinct(ip)')
=> [#<User ip: "80.74.172.18">, #<User ip: "80.74.172.13">, ... ]

As you can see this will give you ActiveRecords with only that attribute initialized. Often you need to do something with those distinct values (and not just display them) so it’s more suitable to have values (instead of ActiveRecords) in an array. Use select values for that:

>> User.connection.select_values('select distinct(ip) from users')
=> ["80.74.172.18", "80.74.172.13", ... ]

10 Rails console tricks

2009-12-20T00:00:00+01:00

Invoking helper methods

>> helper.number_to_currency('123.45')

Method definition finder (irb)

>> helper.method(:truncate)
=> #<Method: ActionView::Base(ActionView::Helpers::TextHelper)#truncate>

>> "".method(:camelize)
=> #<Method: String(ActiveSupport::CoreExtensions::String::Inflections)#camelize>

Method finder (irb)

$ gem install what_methods

>> require 'what_methods'
>> "foo ".what? "foo"
"foo ".chop! == "foo"
"foo ".chop == "foo"
"foo ".strip! == "foo"
"foo ".strip == "foo"
"foo ".rstrip! == "foo"
"foo ".rstrip == "foo"
=> ["chop!", "chop", "strip!", "strip", "rstrip!", "rstrip"]

Method lookup (irb)

>> "".methods.grep(/case/).sort
=> ["camelcase", "casecmp", "downcase", "downcase!", "swapcase", "swapcase!", "titlecase", "upcase", "upcase!"]

Avoid screenfuls of objects (irb)

>> people = Person.all; nil
=> nil

Rollback database modifications on exit

$ ./script/console --sandbox

Last expression (irb)

>> Person.first
=> #<Person id: 1, first_name: "Dejan" ... >
>> _.first_name
=> "Dejan"

Reload code changes

>> reload!

Better object format (irb)

>> y User.first
--- !ruby/object:User 
attributes: 
  hashed_password: 123456789cde83xa9b86e36e4627360
  last_seen_at: 2009-12-09 13:16:44
  username: dejan
  id: "1"
  created_at: 2007-01-14 17:30:00
attributes_cache: {}

script/console logging

You need this.

>> User.cached(:first)
==> Got User:first from cache. (0.10173)
  User Load (300.1ms)   SELECT * FROM `users` LIMIT 1
==> Set User:first to cache. (0.01512)
=> #<User id: 1, username: "dejan", ... >

>> User.cached(:first)
==> Got User:first from cache. (0.00061)
=> #<User id: 1, username: "dejan", ... >

>> User.expire_cache(:first)
==> Deleted User:first from cache. (0.00059)
=> true

Accountability

2009-02-15T00:00:00+01:00

Jay Fields: “I heard once that in Great Britain’s MOD if you design software for a plane you go up in the test plane when the software is beta-tested. If all programmers were held with that level of accountability, how many do you think would still be in our field? How many would you want to collaborate with before you went up in the plane together?”

simple_captcha while developing

2008-10-29T00:00:00+01:00

Type less is my motto these days. Not just the code, but everything.

If you’re developing an app with the excellent simple_captcha plugin do your fingers a favor and monkey patch it in development.rb:

# type less. autosolve captcha while developing
ActionView::Base.module_eval do
  def simple_captcha_field(options={})
    options[:object] ?
      text_field(options[:object], :captcha, :value => simple_captcha_value(simple_captcha_key)) +
        hidden_field(options[:object], :captcha_key, {:value => options[:field_value]}) : 
      text_field_tag(:captcha, simple_captcha_value(simple_captcha_key))
  end
end

Don't escape in Strings

2008-10-26T00:00:00+02:00

So don’t do:

"#{name} said: \"Clap your hands!\""

It’s ugly and you don’t need it. Ruby has excellent support for arbitrary delimiters for string literals.

So above can be rewritten as:

%-#{@name} says: "Clap your hands!"-

… or if String contains dash:

%/#{@name} says: "Play tic-tac-toe!"/

… or if String contains dash and slash:

%Q|#{@name} says: "Try ftp://ruby-lang.org/pub/ruby/1.9/"|

… and so on. No need to escape.

Excerpt from the great book The Ruby programming Language:

“The sequence %q begins a string literal that follows single-quoted string rules, and the sequence %Q (or just %) introduces a literal that follows double-qouted string rules. The first character following q or Q is the delimiter, and the string literal continues until a matching delimiter is found. If the opening delimiter is (, [, {, or <, then the matching delimiter is ), ], }, or >. Otherwise, the closing delimiter is the same as the opening delimiter.”

Alternative join and split in Ruby

2008-07-09T00:00:00+02:00

Join

>> %w(tic tac toe) * "-" 
=> "tic-tac-toe"

Split

>> "tic-tac-toe" / "-" 
=> ["tic", "tac", "toe"]

Unfortunately, for split you’ll need this of course:

class String
  alias / :split
end

;)

Self or default if empty, DRY way

2008-03-19T00:00:00+01:00

I really appreciate following idiom in Ruby:

person.phone || "N/A"

It’s DRY. No need for conditional structures, and repeating person.phone in condition and as return value.

But lets say you don’t control your data source, and there is an empty string instead of nil when data is not available (sounds familiar?). How would you deal with that and keep things simple and DRY?

Well, basicly all you need is a String method that will return nil if string is empty, or self if it’s not empty. String object doesn’t have that kind of method, at least not that specialized. Regexp to rescue. Lets try this:

>> ""[/.+/m]
=> nil

>> "ruby"[/.+/m]
=> "ruby"

Nice. So solution for the problem above is:

person.phone[/.+/m] || "N/A"

Throw andand in game to support both nil and empty value with no cost in complexity:

person.phone.andand[/.+/m] || "N/A"

andand

2008-03-18T00:00:00+01:00

I really, really like andand. Try it and stop repeating yourself.

I mean, why would you want to write this:

entry.at('description') && entry.at('description').inner_text

when you can write this:

entry.at('description').andand.inner_text

Eleventh

2008-02-11T00:00:00+01:00

Did you know that Ruby was Matz’ eleventh take on creating a programming language? Listen. So don’t despare next time you fail, you are right on track.

I sat down and counted the other day and Ruby was eleventh language I’ve tried to write. Out of those 4 only had names, 3 of them didn’t work at all… the rest of them was just experiments. Ruby is the only one that really worked, so I guess that makes Ruby the first one, but it was one out of eleven attempts.

~ Matz

The road to wisdom? – Well, it’s plain and simple to express: Err and err and err again but less and less and less.

~ Piet Hein

Nested Ternary Operator

2008-01-20T00:00:00+01:00

I was going through some of my old Java code and found this interesting piece of code. It’s basically alternative way of creating switch structure.

  public Object getValueAt(int row, int col) {
    Person person = data.get(row);
    return 
      col==0? person.getFirstName() 
      : col==1? person.getLastName() 
      : col==2? person.getAge()            
      : col==3? person.getAddress()
      : null; 
  }

Cons:

unlike switch, there is no compile time error for duplicated cases
this is not a standard way of dealing with different values of a variable so you could leave wondering the person that will read your code

Pros:

more control over branching logic since expressions are used (switch must use constants as case values)
this is not a standard way of dealing with different values of a variable so you could be seen as hacker in the eyes of the person that will read your code ;)

Dejan Simic

Don't wish it were easier

Compiling Ruby on a fresh Lion install

Latest XCode 4.2 does not install (non-llvm) gcc-4.2 anymore

OS X provides the BSD libedit library, which shadows libreadline

Inline logging in Rails console

Kids, don't try this at work

Start the SSH tunnel to your production database

Configure your app to use the tunnel as database

Have some haxor backdoor

Handle subdomains if any

Be fucking careful!

The opposite

Resolve all errors in Hoptoad for free

Release process

espeak-ruby

Demo

Example usage

Features

Sinatra example

Install

Source

Credits

auto_html

Demo

Type or paste URLs

Code

Preview

Example usage

Non-ActiveRecord models

Rake and Capistrano tasks

Bundled filters

Install

Source

Credits

Yesterday's Weather

Distinct values in Rails

10 Rails console tricks

Invoking helper methods

Method definition finder (irb)

Method finder (irb)

Method lookup (irb)

Avoid screenfuls of objects (irb)

Rollback database modifications on exit

Last expression (irb)

Reload code changes

Better object format (irb)

script/console logging

LINKS

Accountability

simple_captcha while developing

Don't escape in Strings

Alternative join and split in Ruby

Join

Split

Self or default if empty, DRY way

andand

Eleventh

Nested Ternary Operator