Notes posted to Ruby on Rails

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June 15, 2011
1 thank


beware, update_all silently ignores :limit and :order option in 3.0.8.

I’ve fixed my code temporarily with

update_all "foo=1 where #{myscope.where_values} limit 1"
June 14, 2011 - (>= v2.3.2)
1 thank

Set ids when using a collection of values

The trick to getting the helper to populate a unique HTML ID and for rails to recognise a collection is to give the helper a unique ‘name’ and to set the :name symbol to parameter with an array symbol ‘[]’.

<% Cars.each do |c| %>
  <%= check_box_tag "car_ids[#{c.id}]", c.id, :name => "car_ids[]" %>
<% end %>
June 10, 2011
0 thanks

Typo in matches? example

Iphone example should be def self.matches?(request)

June 4, 2011 - (>= v3.0.0)
4 thanks

finding without default scopes in rails 3

if you want to find without default scopes in rails 3 and with_exclusive_scope is giving you protected method errors in controllers, use unscoped for a similar purpose

June 1, 2011 - (>= v3.0.0)
0 thanks

Catching rollback and re-raise exception

In response to wiseleyb, I don’t believe that you could put “rescue” in a transaction block, let alone catching ActiveRecord::Rollback. It would lead you to an “unexpected kRESCUE” error.

I think this is more appropriate.

def start_transaction
  Company.transaction do
    # don't forget the bang to make sure it raise
    # exception or the transaction won't rollback

    return true

  # re-raise exception here
  raise "Exception!"

Then you could call the method in another place, and it would raise rollback and other exception.

  # would return the "Exception!" if rollback occurs
  # it would also still trigger another exception other
  # than rollback.
May 31, 2011 - (>= v3.0.0)
0 thanks

return random element

>> a = [1,2,3] >> a.sample 2

the same as

>> a[rand(a.length - 1)] 1

May 26, 2011
0 thanks

Don't Use to_formatted_s(:db) on an Array of IDs

I thought using to_formatted_s(:db) on an array of ids would separate them with commas in a nice way. Wrong. It does, but it also changes the numbers.


[60, 271, 280, 283].to_formatted_s(:db)
# => "121,543,561,567"    # Completely different numbers!

Instead, use the join method:


[60, 271, 280, 283].join(",")
# => "60,271,280,283"      # Much better

I think this has to do with (:db) being used for formatting dates but I’m not sure.

May 24, 2011
2 thanks

must be first

A little gotcha I ran into.

This must be defined before you define your relationships.


class Ticket < ActiveRecord::Base
  set_table_name 'ticket'
  belongs_to :customer
  has_one :account, :through => :customer

if you do the relationships first it will not use the correct table name on the lookups.

May 23, 2011 - (>= v3.0.5)
5 thanks

Change to the way the block is handled

At least in 3.0.5, some of the previous examples no longer work: ActionView seems to quietly ignore Array content.

If you were using code of the form

content_tag(:li, nil, :class => 'someClass') {
  arr.collect { |x|
    content_tag(:ul, x)

it now needs to look like

content_tag(:li, nil, :class => 'someClass') {
  arr.reduce('') { |c, x|
    c << content_tag(:ul, x)
May 20, 2011 - (>= v3.0.0)
0 thanks

relative_url_root= no longer exists in Rails 3.0

Rails 3.0 does this with scope in config/routes.rb

scope "/exampleapp" do
  resources :examples
  root :to => "examples#index"
May 6, 2011
0 thanks

Asserting Emails

–setup_mailer.rb in config/initializers –rails g mailer MailerName –methods in mailer_name.rb –files in views/mailer_name –MailerName.method(@object).deliver in object controller

May 6, 2011
0 thanks

Using OpenID

–rails g nifty:authentication –redo rake db:migrate –add: before_filter :login_required, :except => :index to appropriate controllers.

April 14, 2011
0 thanks

Why gsub!

I notice other adapters use sql.sub!, not sql.gsub! and in fact I had trouble with adding the limit parameter to any query involving nested selects. Replacing sql.gsub! with sql.sub! solved that problem for me. Has anyone else had a similar experience with this method?

In other words, replace:

sql.gsub!(/SELECT/i, 'SELECT B.* FROM (SELECT A.*, row_number() over () AS internal$rownum FROM (SELECT')


sql.sub!(/SELECT/i, 'SELECT B.* FROM (SELECT A.*, row_number() over () AS internal$rownum FROM (SELECT')
April 14, 2011
0 thanks

logging before filters

If you need to track and log which before filters are called for the purpose of debugging your app/before_filters. Then here’s a suggestion, how this could be accomplished:


April 8, 2011
0 thanks

customizing text when using label in a form

Instead of the default text Email you can change it to “Primary Email” like this: f.label :email, “Primary Email”

April 6, 2011 - (v3.0.5)
0 thanks

the source is wrong!

in 3.0.5, the source code in line 15 looks like this:

respond_to?(:"#{k}=") ? send(:"#{k}=", v) : raise(UnknownAttributeError, "unknown attribute: #{k}")

whats wrong with apidock?

April 4, 2011 - (>= v3.0.0)
0 thanks
March 31, 2011 - (v3.0.0 - v3.0.5)
0 thanks

reload is deprecated? what's the new alternative?

What’s the recommended alternative to reload for more recent versions of Rails?

March 30, 2011 - (v3.0.0 - v3.0.5)
2 thanks

After filters are not called when exception occurs

Please note after filters are not executed when an exception occurs. You have to handle these situations explicitly.

March 25, 2011
4 thanks

How to specify :only_path when non-hash options

When passing in an object, as opposed to a hash, you can’t do this because url_for accepts one argument:

url_for(post, :only_path => true)

Instead, do this:

polymorphic_url(object, :routing_type => :path)
March 23, 2011
2 thanks


Note that ActiveRecord will not update the timestamp fields (updated_at/updated_on) when using update_all().

March 23, 2011 - (v3.0.0 - v3.0.5)
0 thanks
March 23, 2011 - (v3.0.0 - v3.0.5)
1 thank
March 22, 2011
0 thanks

Find a random *set* of records (without killing the db)

If you want to find any number of records without sorting your entire table randomly every time, try the solution I posted here:


March 21, 2011 - (v3.0.0 - v3.0.5)
0 thanks
March 16, 2011 - (<= v2.3.8)
0 thanks
March 15, 2011
0 thanks

Don't cache it!

Don’t store a connection in a variable, because another thread might try to use it when it’s already checked back in into the connection pool. See: ActiveRecord::ConnectionAdapters::ConnectionPool

connection = ActiveRecord::Base.connection

threads = (1..100).map do
  Thread.new do
      10.times do
        connection.execute("SELECT SLEEP(1)")  # WRONG
        ActiveRecord::Base.connection.execute("SELECT SLEEP(1)")  # CORRECT
      puts "success"
    rescue => e
      puts e.message

March 14, 2011
0 thanks

formating date

I18n.l Time.now, :format => “%e %B”


March 14, 2011
1 thank

Looking for method "l" and "t"

translate # Lookup text translations localize # Localize Date and Time objects to local formats

These have the aliases #t and #l

look at ActionView::Helpers::TranslationHelper

March 8, 2011 - (v2.3.8 - v3.0.5)
3 thanks

Dont use _delete

Most blog articles about accepts_nested_attributes_for, including the one from @mattsa and @annaswims, tell you to add a

'_delete' => 1

when you want a deletion checkbox, hidden attribute, etc.

But this stopped being true a while ago. This is just a “Watch Out!” Make sure you use

'_destroy' => 1