Ever wondered how to get your time-dependent scopes to act like bunch of lunatics? 

do this: 

class User < ActiveRecord::Base

 scope :active, where(:activated_at.gt => Time.now)

end

and your list of active users will stub every time you restart your app. Cool!

Of course, this great trick can’t be achieved with this:

class User < ActiveRecord::Base

 scope :active, lambda{ where(:activated_at.gt => Time.now) }

end

Sql injection is a very nice trick, however it’s really hard to achieve with Rails. This few simple lines of code allow all of your users to execute sql whatever way they want:

#app/models/user.rb
class User < ActiveRecord::Base

  scope :very_clever_scope, lambda{|name_or_id| where("name = #{name_or_id} OR id=#{name_or_id}") 

end

#app/controllers/users_controller.rb
class UsersController < ApplicationController 

  def show
    #uber clever params[:id] backwards compability
    User.very_clever_scope(params[:id]).find(:first)
  end

end

And now you can relax and enjoy DROP ALL TABLES queries.

This great tip allows you to recursively set hash value - really useful thing when you have to generate complicated hash. 

One gotcha that i found about this is, that after generating SuperHash instance you must remember about reseting the default value of this hash.

Consider this: 

 
class SuperHash < Hash   
  def initialize     
    super { |h, k| h[k] = SuperHash.new }   
  end 
end  
> suuper = SuperHash.new #=> {} 
> suuper['mad']['sheep'] = false    
> suuper['mad']['sheep'] #=> false 
> suuper['mad']['cow'] #=> {} 
> supper['calm']['sheep'] #=> {} 

Notice that every undefined key, no matter how deeply nested will return empty hash instead of nil. This was a bit misleading for me since i used SuperHash instance to check complex conditions

 > !!{} #=> true 

Whatever i did, all conditions were always true :)

The solution of course w’d be to reset SuperHash default after generating full structure:

 
> suuper = SuperHash.new #=> {} 
> suuper['mad']['sheep'] = false
> suuper.default = nil #=> nil
> supper['calm']#=> nil

However, as my colleague pointed out, reseting default only on suuper wont fix the issue, since nested hashes inside still have their own defaults. What we need to do is complete rewrite of our superhash back to hash again. This can be easily achievied with this:

 
> suuper = SuperHash.new #=> {} 
> suuper['mad']['sheep'] = false #=> false
> suuper = {}.update(suuper)
> supper['calm'] #=> nil
> suuper['mad']['cow'] #=> nil
> supper['calm']['sheep'] #=> Error

And now we are golden :)

4 steps to resolve:

1. sudo apt-get install ncurses-dev
2. cd $HOME/.rvm/src/ruby-1.9.2-p180/ext/readline
3. ruby extconf.rb — —with-readline-dir=”$HOME/.rvm/usr”
4. make install

More information:
http://beginrescueend.com/packages/readline/

Since most of us use macs and most of us work on few projects at the same time we really appreciate what 37signals did. Go and check out Pow project.

There is an interesting initiative coming from Spain. The idea is to put humans.txt file containing information about people who have contributed to building the site. More at humanstxt.org

You must update to 1.9.2. RoR3 applications on old ruby are slow. REALLY SLOW.

Watchout for serialized fields in ActiveRecord. On ruby 1.9.2 strings in such fields get saved with ASCII-8BIT encoding, not with UTF-8 as you w’d expect.

Since we use coffeescript at netguru for some time now, we c’d sit back and relax while entire RoR community was burning in the hot fire of this flame.

Our favourite pics from the comments:

http://is.gd/HJK6sJ

http://is.gd/NZuBtX

http://is.gd/qTNFdT

http://is.gd/SeN28X 

http://is.gd/CBbcJH

http://is.gd/UTSAtX

And this one pretty much sums it up:

http://is.gd/QUlhVZ

:)