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October 8, 2011
6 thanks

Undocumented :location option

You can use undocumented :location option to override where respond_to sends if resource is valid, e.g. to redirect to products index page instead of a specific product’s page, use:

respond_with(@product, :location => products_url)  
October 7, 2011
3 thanks

How to submit current url

For example to change some kind of param on select change…

<%= form_tag({}, {:method => :get}) do %>
  <%= select_tag :new_locale, options_for_select(I18n.available_locales, I18n.locale), :onchange => "this.form.submit();" %>
<% end %>
October 6, 2011
1 thank

Difference in the way returns are handled

Also, there is a difference in the way returns are handled from the Proc. A return from Proc.new returns from the enclosing method. Return in lambda-block acts like in regular method.

return example

def proc_return
  Proc.new { return "Proc.new"}.call
  return "proc_return method finished"

def lambda_return
  lambda { return "lambda" }.call
  return "lambda_return method finished"
puts proc_return
puts lambda_return
# => Proc.new
# => lambda_return method finished
October 4, 2011
1 thank

Unexpected rounding behavior

Both 2.5 and 1.5 are rounded to 2…

ree-1.8.7-2010.02 > sprintf("%.f", 0.5) 
=> "0" 
ree-1.8.7-2010.02 > sprintf("%.f", 1.5)
=> "2" 
ree-1.8.7-2010.02 > sprintf("%.f", 2.5)
=> "2" 
ree-1.8.7-2010.02 > sprintf("%.f", 3.5)
=> "4" 
ree-1.8.7-2010.02 > sprintf("%.f", 4.5)
=> "4" 

use round instead to get proper behavior

October 4, 2011
2 thanks

How to change format automatically depending on locale...

… without passing locale option.

In your application_helper.rb (or in other helper) place following code:

def number_to_currency(number, options = {})
  options[:locale] ||= I18n.locale
  super(number, options)

Then, in your locale files:

        format: "%n %u"
        unit: "USD"

And that is it :)

October 3, 2011 - (>= v1_9_1_378)
0 thanks

example will not work in 1.9+

Since 1.9 introduces native threads, we cannot assume the order of exectution and the example above is not thread safe and fails with a “deadlock detected (fatal)” error. Also Thread.pass is pointless in the context of native threads.

This will work as intended with native threads:

a = Thread.new { print "a"; Thread.stop; print "c" } 
sleep(0.1) until a.status == 'sleep'
print "b"
October 3, 2011
0 thanks


If you’re actually looking to cut down on code why not use .map instead of the longer .collect?

September 30, 2011 - (>= v3.0.0)
1 thank

Using a block with image_tag

HTML5 officially supports block-level elements in the anchor tag and Rails 3 allows you to pass a block to image_tag:

<%= image_tag(some_path) do %>

<%= content_tag(:p, "Your link text here")

<% end %>

September 30, 2011 - (v3.0.0 - v3.1.0)
0 thanks

Without module

If you want to have only the path prefix without namespacing your controller, pass :module => false.


namespace :account do
  resources :transactions, :only => [:index]

account_transactions GET /account/transactions(.:format)
{:controller=>"account/transactions", :action=>"index"}

With :module => false:

namespace :account, :module => false do
  resources :transactions, :only => [:index]

account_transactions GET /account/transactions(.:format)
{:controller=>"transactions", :action=>"index"}
September 29, 2011 - (v2.0.0 - v3.1.0)
2 thanks

Additional Format meaning

%e - Day of the month, without leading zero (1..31)

September 27, 2011 - (>= v3.1.0)
0 thanks

1.9 behavior

“In Ruby 1.9 and newer mb_chars returns self’”

This would seem to be a lie. At least in rails 3.1.0 and ruby 1.9.2, mb_chars still returns a proxy object with additional useful methods defined on it that aren’t on a 1.9.2 String.

ruby-1.9.2-p180 :007 >  "àáâãäå".normalize(:kd)
NoMethodError: undefined method `normalize' for "àáâãäå":String

ruby-1.9.2-p180 :008 > "àáâãäå".mb_chars.normalize(:kd)
 => àáâãäå
September 25, 2011
1 thank

Parsing the Date Params into a New Date Object.

Useful for when you need to create a Date object from these manually, such as for reporting.

If the date select input is start_date and it belongs to the report form object:

@start_date = Date.civil(params[:report]["start_date(1i)"].to_i,

# => Date

# => Sun, 25 Sep 2011  # For example.

Use a similar method for DateTime situations.

September 17, 2011
0 thanks

this works, but doesn't make sense

does it?

replace(klass.find(ids).index_by { |r| r.id }.values_at(*ids))



I see no point in making it that complicated

September 15, 2011
2 thanks

beware of trying to dup in subclass inside class context

The example of adding to an array without effecting superclass:

# Use setters to not propagate changes:
Base.setting = []
Subclass.setting += [:foo]

That’s right as far as it goes. But beware when you are in context of class definition:

class Subclass < Base
   # possibly wrong, ruby seems to get 
   # confused and think you mean a local 
   # var, not the class ivar
   setting += [:foo]

   # But this will work:
   self.setting += [:foo]

   # Or:
   self.setting = self.setting.dup
   self.setting << :foo

September 14, 2011
0 thanks

Find a Selected Option in a Drop Down.

You can find the selected option (or options for multiple select inputs) with the following:

assert_select('select#membership_year option[selected]').first['value']
September 14, 2011
2 thanks

More on add_to_base

Actually, use

model_instance.errors.add :base, :invalid

to have I18n working.

September 13, 2011
0 thanks

more options

useful options are:

:root => ‘object’, :skip_instruct => true, :indent => 2

:builder can also be used to pass your own Builder::XmlMarkup instance.

September 13, 2011
1 thank

Some unexpected behaviour

When using Array as default value, it behaves more like cattr_accessor

class A
 attr_accessor_with_default :b, []

x = A.new
x.b << 1

#puts x.b.inspect => [1]

y = A.new
y.b << 2

#puts y.b.inspect => [1, 2]
September 9, 2011 - (v3.0.9)
0 thanks

Example usage...


Time.now.advance(:days => +2, :hours => +8)


September 8, 2011 - (>= v3.0.9)
0 thanks

First example simplified

The first code example may be simplified, since the call to method to_xml is made implicitly anyway:

def index
  @people = Person.find :all

  respond_to do |format|
    format.xml { render :xml => @people }
September 7, 2011 - (v3.0.0 - v3.0.9)
0 thanks

Tested w/ Rails 3 and returning true/false ignored

Per http://ar.rubyonrails.org/classes/ActiveRecord/Callbacks.html “If a before_* callback returns false, all the later callbacks and the associated action are cancelled. If an after_* callback returns false, all the later callbacks are cancelled.” [and presumably associated action is not canceled]

So, the callback chain will be broken, but the save will still happen.

Also ran into this: http://innergytech.wordpress.com/2010/03/08/dont-put-validations-in-after_save/

September 7, 2011 - (>= v3.0.9)
0 thanks

Passing an object as argument

It is possible to pass an instance of a record to the method. See the documentation of polymorphic_url (http://apidock.com/rails/ActionDispatch/Routing/PolymorphicRoutes).

September 5, 2011
1 thank

(Another) Pluralize Without Showing the Count

Thought it would be best to take the source code from pluralize and just remove the count from the output.

Create this helper method in application_helper.rb

# Pluralize without showing the count.
def simple_pluralize count, singular, plural=nil
  ((count == 1 || count =~ /^1(\.0+)?$/) ? singular : (plural || singular.pluralize))

This allows you to pass in in the plural word to use as well.

August 30, 2011 - (>= v3.0.0)
1 thank

Does not work for has_one associations

If you are using this to validate that a has_one association has been made with another object this will not work, as the test used in the AssociatedValidator #validates_each method tests for nil and then ignores this object.

To test for association with a has_one association you can use the following code:

validate do
  [:teacher, :book].each do |attr|
    errors.add(attr, "is required") if self.send(attr).nil?
August 23, 2011
0 thanks

the correct return value of html_escape in example above

the correct return is:

# => is a &gt; 0 &amp; a &lt; 10?

August 19, 2011
0 thanks

Alternative way to show relative paths from absolute globbing

An alternative to show relative paths is using the well known String#sub! method

base_dir = File.expand_path("my_dir") << "/" # don't miss adding "/"
files = Dir[File.join(base_dir, '**', '*.html.gz')]
p files.map {|f| f.sub!(base_dir,"")}
August 15, 2011
1 thank

The :path option

The path option will actually set the path and not the prefix I have found in Rails 3.0.5.


resources :my_reports, :path => 'my-reports'

All actions for this resource will now be at /my-reports.

August 14, 2011
0 thanks

Security issue

One thing to note about the code above is that it could have a security issue. If the user changes his/her password, the authentication token should expire. Hence, in a production scenario you should put in the password salt or something to allow the token to become invalidated.

August 14, 2011
1 thank

stub/stub! will always be followed by '.and_return'

this function will aways be followed by ‘.and_return(…)’ because a stub is typically used for returning values. The required argument given to stub is a method name. When a message to this stubbed method name is received by a class or existing object of the class AND ‘.and_return’ is provided, the stub will return whatever was provided as argument to ‘.and_return’.

For example,


  • this will return 5.5% when a message for interest_rate in a HomeLoan class’s object is received.

HomeLoan.stub!(interest_rate).and_return(‘5.5%’, ‘3%’)

  • this will return 5.5% when a message for interest_rate in a HomeLoan class’s object is received FOR THE FIRST TIME but will return 3% for subsequent calls/messages.