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10 Rails console tricks

Dejan Simic — Sun, 20 Dec 2009 00:00:00 +0000

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

Editing /etc/hosts on Mac OS

Dejan Simic — Tue, 24 Mar 2009 00:00:00 +0000

I almost killed my macbook until I figured this out. In Linux there’s no need for this, but on Mac OS, after editing /etc/hosts in order to immediately apply changes you must run this:

lookupd -flushcache

Accountability

Dejan Simic — Sun, 15 Feb 2009 00:00:00 +0000

“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?”

—http://blog.jayfields.com/2009/01/cost-of-net-n…

auto_html plugin

Dejan Simic — Fri, 13 Feb 2009 00:00:00 +0000

Read more about my new Rails plugin on company’s blog:
http://www.elctech.com/projects/auto_html-plugin

Random Haml tips

Dejan Simic — Sat, 31 Jan 2009 00:00:00 +0000

I’ve just shared my love to Haml on company’s blog:
http://www.elctech.com/articles/random-haml-tips

My pet is growing

Dejan Simic — Wed, 14 Jan 2009 00:00:00 +0000

On this day, exactly two years ago I’ve deployed the first public release of something that is best described as “urbandictionary.com in Serbian”.
Some interesting facts:

vukajlija.com is inspired by urbandictionary.com and built on Rails. I’ve recently found out that urbandictionary.com switched from PHP to Rails.
vukajlija.com is still just my pet project. I’m not earning any money from it, but it pays its own bills. I’m working on it when I find free time for fun and to gain more experience with Ruby and Rails.
vukajlija.com has a constant growth in visits and pageviews for the past 16 months.

Rails SEO Starter Guide

Dejan Simic — Wed, 19 Nov 2008 00:00:00 +0000

I’ve just posted Rails SEO Starter Guide on company’s blog. Go check it out.

simple_captcha while developing

Dejan Simic — Wed, 29 Oct 2008 00:00:00 +0000

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

Dejan Simic — Sun, 26 Oct 2008 00:00:00 +0000

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.”

So create

Dejan Simic — Fri, 29 Aug 2008 00:00:00 +0000

Alternatives

Dejan Simic — Mon, 18 Aug 2008 00:00:00 +0000

A year ago, I got interested in alternatives, and started switching:

~~erb~~ => haml
~~test_unit~~ => rspec
~~prototype/scriptaculous~~ => jQuery
...

mental note to myself: stay the hell away from merb! ;)

Alternative join and split in Ruby

Dejan Simic — Wed, 09 Jul 2008 00:00:00 +0000

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

Dejan Simic — Wed, 19 Mar 2008 00:00:00 +0000

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

Dejan Simic — Tue, 18 Mar 2008 00:00:00 +0000

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

Dejan Simic — Mon, 11 Feb 2008 00:00:00 +0000

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

Dejan Simic — Sun, 20 Jan 2008 00:00:00 +0000

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 ;)