Concerning greeneggs614's post:

The following version would be a bit more intention revealing while providing the same output:

<% Car.each do |c| %>
<%= check_box_tag "car_ids[]", c.id, :id => "car_ids_#{c.id}" %>
<% end %>

==== Only does SELECT model.id FROM models_table

regardless of select options

The clue here is that you actually specify the prompt on the select element, and not in the option_groups_from_collection_for_select element.

<%= f.select :post_type_id,   option_groups_from_collection_for_select(@categories, :post_types, :name, :id, :name), :include_blank => "Please select..."...

Simple but thought it was worth mentioning:

( [ 1, 2, 3 ] + [ 3, 4, 5 ] ).uniq    #=> [ 1, 2, 3, 4, 5 ]

I use this in views when I need to join a array of objects from a sql request here is a basic version of what I mean.

==== Code example

<%= @blogs.map{ |blog| blog.comment }.join(" | ") %>

This function, available on any Base derived class, allows eager loading. So when iterating over a result, all the data can be pre-cached, reducing the number of queries from 1+x to 2.

Several ways to use this include:

Post.includes(:author).where(..)

Post.includes([:author, :comments]).where(.....

I would just use the path_to_image. I find that this is what works best. As it says above it can create problems.

Here is my code

==== Code example

def background_path(background)
if background
  path_to_image background.file_name.normal
else
  path_to_image "background_previ...

sample randomly picks 1 or n elements from the array

==== is_running.rb:

#!/usr/bin/env ruby

pid = ARGV[0].to_i

begin
Process.kill(0, pid)
puts "#{pid} is running"
rescue Errno::EPERM                     # changed uid
puts "No permission to query #{pid}!";
rescue Errno::ESRCH
puts "#{pid} is NOT running.";...

['one','two','three'].to_sentence

=> "one, two, and three"

I had to dig around to find this out - if you want to use memoize somewhere, like an ActiveRecord model, you need to add

extend ActiveSupport::Memoizable

to the class. This doesn't seem to be explained anywhere (the only docs are 3 year old blog posts anyway).

Plumba, it's not that useless if you think about possibility to change a hidden field with JS

Actually, this method is not available now.(https://github.com/ruby/ruby/blob/trunk/rational.c#L2352)

Mostly, the database date columns are DateTime instances. Whereas Rails adds several useful utility functions to DateTime (in activesupport), there is some confusing behavior. This is at least somewhat surprising.

Two subtract two DateTime instances, you should always "round" the returned value. Su...

This method was moved to AbstractController::Callbacks, as stated on [1].

It took me a while to figure out 'what should I use instead before_filter'. Hope this helps anyone that hits the same road I'm in.

[1] - http://stackoverflow.com/a/7129460/1040571

@ssoroka even I'm having same issue. how did you resolve it?

It is nice to know, that you can store any custom configuration key in configure block... E.g.

YourApp::Application.configure do
 # ...
 config.my_custom_setting = "QWERTY1234"
end

Then you can just access it by calling

YourApp::Application.config.my_custom_setting

As request.request_uri has been deprecated, use

request.url

instead.

I noticed that cloning an active record object in ruby-1.9.3 and then changing an attribute on the original object will actually change the cloned object as well. This was not the case in ruby-1.9.2.

a.flat_map(&b) works exactly like a.map(&b).flatten!(1).