Notes posted to Ruby on Rails

be aware that this writes to tmp/cache

Its supposed to be http caching, but Rails will actually cache the response to whatever you specified as the cache store, *as well*, but only if you specify :public => true. The default is filestore so it will try to write to tmp/cache.

Only a problem if you don’t have the proper permissions set, in that scenario your apache/nginx logs could fill up very quickly with “permission denied errors”

Full explanation is here http://blog.tonycode.com/archives/418

increment_by_sql for PG

Note, if you’re using the code below for incrementing by SQL with a Postgres database, it’s not going to like the backticks. Just remove them:

def increment_with_sql!(attribute, by = 1)
  raise ArgumentError("Invalid attribute: #{attribute}") unless attribute_names.include?(attribute.to_s)
  original_value_sql = "CASE WHEN #{attribute} IS NULL THEN 0 ELSE #{attribute} END"
  self.class.update_all("#{attribute} = #{original_value_sql} + #{by.to_i}", "id = #{id}")
  reload
end

Use concat insted of joining collection explicitely

concat method will be useful to join the collection object from looping conditions.

arr = ["a", "b", "c"]
content_tag(:ul, :class => 'a class') do
  arr.each do |item|
  concat content_tag(:li, item)
end

And this will generate the html as shown below

<ul class="a class">
  <li>a</li>
  <li>b</li>
  <li>c</li>
</ul>

Edge case

.

Edge case

Have look how #between? handle adge case. It’s different from DateTime’s.

Date.yesterday.between?(Date.yesterday, Date.tomorrow)
=> true

Date.tomorrow.between?(Date.yesterday, Date.tomorrow)
=> true

When dealing with has_many through

The non-repeating primary key id must be used with find_in_batches.

• User has many things

• User has many socks through things

• Sock has many things

• Sock has many users through things

For the sake of argument, assume the first user has two socks and all other users have one sock. There are 1000 users in total and 1001 socks in total.

User.joins(:socks).count
=> 1001
agg = []
# Incorrect
User.joins(:socks).find_in_batches{|g| agg += g}
agg.count
=> 1000

Sock.joins(:users).count
=> 1001
agg = []
# Correct
Sock.joins(:users).find_in_batches{|g| agg += g}
agg.count
=> 1001

Out of date for Rails 3.

This is out of date for Rails 3; instead see ActiveRecord::Persistence#update_attributes

Beware - May cause performance issues

A serialized attribute will always be updated during save, even if it was not changed. (A rails 3 commit explains why: http://github.com/rails/rails/issues/8328#issuecomment-10756812)

Guard save calls with a changed? check to prevent issues.

class Product < ActiveRecord::Base
  serialize :product_data
end

bad

product = Product.first
product.save

good

product = Product.first
product.save if product.changed?

Exceptions raised within are ignored.

From http://guides.rubyonrails.org/active_record_validations_callbacks.html

The after_commit and after_rollback callbacks are guaranteed to be called for all models created, updated, or destroyed within a transaction block. If any exceptions are raised within one of these callbacks, they will be ignored so that they don’t interfere with the other callbacks. As such, if your callback code could raise an exception, you’ll need to rescue it and handle it appropriately within the callback.

Default field order

If you want to set an app wide default order for the fields (rather than passing :order each time), use the locale file.

eg. edit config/locale/en.yml to include:

en:
  date:
    order: 
      - :day
      - :month
      - :year

Checking content_for

There’s a much simpler way to check if content exists or not, and it’s been provided as example in docs since 05.2010:

module StorageHelper
  def stored_content
    content_for(:storage) || "Your storage is empty"
  end
end

But this behavior was broken with SafeBuffer. You’ll be able to use it again when this issue (github.com/rails/rails/issues/9360) will be fixed and merged with master.

It also works with strings

It works with strings:

ActiveRecord::Base.connection.column_exists?('users', 'id')

Which is helpful if you need to specify the database/schema to use:

ActiveRecord::Base.connection.column_exists?('secondary.users', 'id')

conditional rescue from does not seem working on Rails 3.2.11

Be careful, conditional rescue_from does not work in Rails 3.2.11

The purpose of this method

This method keeps track of whether a hidden id field needs to be created when the form builder is generating fields for a nested model. It gets set to true by #hidden_field when that method is used to create a field named ‘id’.

Here’s an example of what this can be useful for: http://railsforum.com/viewtopic.php?id=39640

Your scope cannot be called 'locked'

• see: http://github.com/rails/rails/issues/7421

• see: http://github.com/rails/rails/pull/6985

  class Article < ActiveRecord::Base
    scope :locked, where(...
  end
  

will cause intermittent problems of the type

undefined method 'locked' for #<Class:0x007fdab3025298>

Use something like ‘access_locked’ instead

Other Example

##

class Exam
 cattr_reader :code, :description, :points, :instance_reader => false

 @@code = "EXM"
 @@description = "Sent Exam"
 @@points = 1000
end

In this case it’s possible to use

Exam.code # => EXM
Exam.description # => Sent Exam
Exam.points # => 1000

Works also with Mongoid

What works for Active Record, also works for Mongoid:

de:
  mongoid:
    attributes:
      picture:
        explanation: Description

Use sqlite3, not sqlite

Note that typically if you want to connect to an SQLite database the adapter would be “sqlite3”; not “sqlite” as depicted in the documentation above. Just using the term “sqlite” might result in the error message: “database configuration specifies nonexistent sqlite adapter”

Using an unobtrusive Ajax (UJS) :onchange call to the controller#action

An :onchange call can be made using the Rails 3 jquery-ujs helper in the form:

check_box_tag( name, value, checked, html_and_other_options)

For example:

select_tag( "my_tag_id", entity.id,
  class: "progress bar update_msg", disabled: disabled?
  data: {
    remote: true,
    url: url_for( action: :my_controller_action, id: my_id)
    // application symbols
    progress_bar: "progress_bar_div_id",
    update: "message_div_id"
  }
)

The jquery_ujs looks for data-remote and data-url. These can be spelled-out or placed in the data hash. The url must be formed as select_tag does not call url_for, unlike some of the other related tags. Values for application symbols can also be passed through. jQuery triggers will work on the Ajax events that occur. This generates the following:

<input class="progress_bar update_msg" data-progress-bar="progress_bar_div_id" data-remote="true" data-update="message_div_id" data-url="/my_controller/my_controller_action/my_id" id="my_tag_id" name="my_tag_id" type="checkbox" value="4"/>

In this example, by tying into the events the program makes visible an existing hidden progress bar while awaiting a server response, and then displays a div containing a message returned by the server and hides the progress bar. If the div contains a class= for notice or error, then they will fade out.

$(".layout")
  .on('ajax:beforeSend', ".progress_bar", function(){ 
    // get id of element to make visible
    var progress_bar_id = '#' + this.getAttribute('data-progress-bar');
    $(progress_bar_id).show();
  })
  .on('ajax:complete', ".progress_bar", function(){ 
    // get id of element to hide
    var progress_bar_id = '#' + this.getAttribute('data-progress-bar');
    $(progress_bar_id).hide();
  })
  .on('ajax:complete', ".update_msg", function(evt, xhr, options){ 
    // get id of element to contain message
    var update = this.getAttribute('data-update'); 
    $("#" + update).replaceWith($(xhr.responseText).attr("id", update));
    // cause responses with these classes to fade away...
    $('.notice').fadeOut(2500);
    $('.error').fadeOut(8000);
  });

for rails >= 3

template_root= is deprecated, use prepend_view_path instead

source: ActionMailer/DeprecatedApi/ClassMethods/template_root

Some documentation available in RailsGuides

The Rails engines getting started guide discusses the usage of isolate_namespace: http://edgeguides.rubyonrails.org/engines.html

Minor edit of pluralize_without_count

patrickberkeley’s method works great. I corrected the grammar a bit for inflection (the singular error).

application_helper.rb

def pluralize_without_count(count, noun, text = nil)
  if count != 0
    count == 1 ? "an #{noun}#{text}" : "#{noun.pluralize}#{text}"
  end
end

This should work in much older versions of Rails also.

Helper Methods inside of a Controller

When needing to include a helper method inside of a controller, instead of including the ENTIRE helper module, simply use this method like so:

module ApplicationHelper
  def fancy_helper(str)
    str.titleize
  end
end

class MyController < ApplicationController
   def index
     @title = view_context.fancy_helper "dogs are awesome"
   end
end

Changing time/date separators

@hayafirst — it is possible to remove that “:” or change it to something else. Just pass `:time_separator` option. Inspect ActionView::Helpers::DateTimeSelector#separator method for more.

Using an unobtrusive Ajax (UJS) :onchange call to the controller#action

An :onchange call can be made using the Rails 3 jquery-ujs helper in the form:

select_tag( name, option_tags, misc_html_options, html_5_data-stuff)

For example:

select_tag( "my_tag_id", get_ids(@entity), class: "progress_and_message",
  data: {
    remote: true,
    url: url_for( action: :my_controller_action, id: my_id)
    // application symbols
    progress_bar: "progress_bar_div_id",
    update: "message_div_id"
  }
)

The jquery_ujs looks for data-remote and data-url. These can be spelled out or placed in the data hash. The url must be formed as select_tag does not call url_for, unlike some of the other related tags. Values for application symbols can also be passed through. jQuery triggers will work on the Ajax events that occur. This generates the following:

<select class="progress_and_message" data-progress-bar="progress_bar_div_id" data-remote="true" data-update="message_div_id" data-url="/my_controller/my_controller_action/my_id" id="my_tag_id" name="my_tag_id"><option value=etc...></option>

For example, tying into the events in this case the program makes visible an existing hidden progress bar while awaiting a server response, and then displays a div containing a message returned by the server and hides the progress bar. If the div contains a class= for notice or error, then they will fade out.

$(".layout")
  .on('ajax:beforeSend', ".progress_and_message", function(){ 
    // get id of element to make visible
    var progress_bar_id = '#' + this.getAttribute('data-progress-bar');
    $(progress_bar_id).show();
  })
  .on('ajax:complete', ".progress_and_message", function(evt, xhr, options){ 
    // get id of element to contain message and to hide
    var update = this.getAttribute('data-update'); 
    var progress_bar_id = '#' + this.getAttribute('data-progress-bar');
    $("#" + update).replaceWith($(xhr.responseText).attr("id", update));
    $(progress_bar_id).hide();
    // cause responses with these classes to fade away...
    $('.notice').fadeOut(2500);
    $('.error').fadeOut(8000);
  });

Example

NOTE: you pass all the keys and values in one long list:

fruit = ActiveSupport::OrderedHash[
  'apple',      'Apple',
  'banana',     'Banana',
  'kiwi',       'Kiwi fruit',
]

fruit.keys => ["apple", "banana", "kiwi"]

Now called class_attribute in Rails 3.2.x

See github.com/novafabrica/make_exportable/pull/4

you will be redirect to signin, when you want to create post before signin

code

def test_should_signin_first_before_add_post
  get "/admin/posts/new"
  follow_redirect!
end

post user authentication info to sessions create action

post_via_redirect(“sessions”, {:user=>{:email=> user.email, :password => user.password}})

Beware: virtual attributes are ignored

Even though validations are called, virtual attributes are ignored.