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Good notes posted to Ruby on Rails

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September 11, 2008 - (v1.2.0 - v2.1.0)
4 thanks

Information on 'ModelName.transaction'

If you are looking for information about:

ModelName.transaction do
  ...
end

or

transaction do
  ...
end

see ActiveRecord::Transactions::ClassMethods

September 11, 2008 - (v1.2.0 - v2.1.0)
4 thanks

Information on 'ModelName.transaction'

If you are looking for information about:

ModelName.transaction do
  ...
end

or

transaction do
  ...
end

see ActiveRecord::Transactions::ClassMethods

September 10, 2008
4 thanks

Be careful with overriding dynamic attribute based finders

don’t try something like this:

class Foo < ActiveRecord::Base
  def self.find_by_bar(*args)
    foo = super(*args)
    raise SomeCustomException unless foo
    foo
  end
end

In newer versions of rails, method_missing defines find_by_bar when you first use it. By calling super, you’re triggering method_missing and overwriting your custom definition! It will work the first time then break! Manually write the call to find!

September 9, 2008 - (<= v2.1.0)
4 thanks

Reset a form

To reset a form easily you can do the following:

page["formid"].reset
September 5, 2008
6 thanks

Custom collection local variable name

Regarding the previous note from hoodow about using :variable_name to create a custom local variable name when rendering a collection with a partial, the argument should be :as instead of :variable_name, so:

render :partial => “video_listing”, :collection => @recommendations, :as => :video

September 5, 2008 - (v1.0.0 - v2.0.3)
3 thanks

This method has moved

To help anyone else looking, this method is now on the ActionView::Template class.

September 4, 2008
5 thanks

Testing protected controllers

When testing controllers which are protected with #authenticate_or_request_with_http_basic this is how you can supply the credentials for a successful login:

@request.env["HTTP_AUTHORIZATION"] = "Basic " + Base64::encode64("username:password")

Must be set before the request is sent through #get or whatever method.

September 2, 2008
5 thanks

Useful in migrations

The most common usage pattern for this method is probably in a migration, when just after creating a table you want to populate it with some default values, eg:

class CreateJobLevels < ActiveRecord::Migration
  def self.up
    create_table :job_levels do |t|
      t.integer :id
      t.string :name

      t.timestamps
    end

    JobLevel.reset_column_information
    %w{assistant executive manager director}.each do |type|
      JobLevel.create(:name => type)
    end
  end

  def self.down
    drop_table :job_levels
  end
end
September 1, 2008 - (>= v2.1.0)
5 thanks

ActiveRecord::Base.include_root_in_json

From Rails 2.1 onwards, the variable

ActiveRecord::Base.include_root_in_json

affects how the JSON is generated. If this is true (default), then the JSON isn’t like the one above. Instead you’ll get:

konata = User.find(1)
konata.to_json
# => { "user": { "id": 1, "name": "Konata Izumi", "age": 16,
      "created_at": "2006/08/01", "awesome": true}}

(Note the model name is included as a root of the JSON object)

For Rails 2.1 generated projects, you’ll see this in the config/initializers/new_rails_defaults.rb file. You’ll need to set the value to false if you want the old behaviour.

ActiveRecord::Base.include_root_in_json = false
August 29, 2008
10 thanks

Always pass a block

I highly recommend always taking a block and passing it back up the chain if you use alias_method_chain, even if the original method does not. Otherwise you’re keeping anyone later in the chain from adding support for blocks.

http://tech.hickorywind.org/articles/2008/08/29/always-pass-a-block-when-using-alias_method_chain

August 29, 2008
5 thanks

Brazilian Real (R$ 1.200,95)

helper:

def number_to_currency_br(number)
  number_to_currency(number, :unit => "R$ ", :separator => ",", :delimiter => ".")
end
August 28, 2008
9 thanks

Get year to show in descending order (Today to 1920 for example)

The way people think of time start and end would be 1920 to today. This made me think “but I want it show the current year first then down.” Well it’s as simple as swapping the start_year and end_year.

date_select :date, :start_year => Date.current.year, :end_year => 1920

# => 2008, 2007, 2006, 2005 ... 1920
August 28, 2008
3 thanks

Moved to ActiveRecord::Calculations::ClassMethods

It appears that this method has simply been moved to the module ActiveRecord::Calculations::ClassMethods. You can still use the example listed in the docs here, it will simply call the method ActiveRecord::Calculations::ClassMethods#count.

August 28, 2008 - (v2.1.0)
3 thanks

When using RESTful routes

I had issues using expire_page with RESTful controllers when expiring anything other than the index action because I was basing my expire_page calls off this example.

The solution is to use my_resource_path for example when User with id 5 is updated, you would have to do:

expire_page user_path(user) # or
expire_page formatted_user_path(user, :xml)

This may apply to early versions but I have only tested on v2.1.0

August 27, 2008
16 thanks

Only attr_accessible attributes will be updated

If your model specified attr_accessible attributes, only those attributes will be updated.

Use attr_accessible to prevent mass assignment (by users) of attributes that should not be editable by a user. Mass assignment is used in create and update methods of your standard controller.

For a normal user account, for example, you only want login and password to be editable by a user. It should not be possible to change the status attribute through mass assignment.

class User < ActiveRecord::Base
  attr_accessible :login, :password
end

So, doing the following will merrily return true, but will not update the status attribute.

@user.update_attributes(:status => 'active')

If you want to update the status attribute, you should assign it separately.

@user.status = 'active'
save
August 26, 2008
6 thanks

Prototype hinted_text_field application_helper

Place this in your helper. It will show a message inside the text box and remove it when someone clicks on it. If they don’t enter a value when they leave the field it’ll replace the message. (Requires javascript :defaults).

def hinted_text_field_tag(name, value = nil, hint = "Click and enter text", options={})
  value = value.nil? ? hint : value
  text_field_tag name, value, {:onclick => "if($(this).value == '#{hint}'){$(this).value = ''}", :onblur => "if($(this).value == ''){$(this).value = '#{hint}'}" }.update(options.stringify_keys)
end

# inside form_for example

hinted_text_field_tag :search, params[:search], "Enter name, brand or mfg.", :size => 30  
# => <input id="search" name="search" onblur="if($(this).value == ''){$(this).value = 'Enter name, brand or mfg.'}" onclick="if($(this).value == 'Enter name, brand or mfg.'){$(this).value = ''}" size="30" type="text" value="Enter name, brand or mfg." />
August 26, 2008
8 thanks

Customizing prompt

The :prompt option not only accepts a boolean value. It can also be given a string to define another than the standard prompt ‘Please select’. Referring to the example it could read:

collection_select(:post, :author_id, Author.find(:all),
                  :id, :name_with_initial,
                 {:prompt => 'Please select the author of this post'})
August 25, 2008 - (v1.1.6 - v2.1.0)
3 thanks

Delete collections with check box tags

Following autonomous’ directions works wonders on /edit but needs slight modifications when dealing with pagination on /index.

In a /index type listing page we can no longer assume that the list of ids coming back represents changes to all objects so we need to provide some context, that the list of object modifications in our params array is a list of modifications for some set of objects.

We can only assume subsets because pagination or filtering may reduce the set of objects we’re working on.

In our case we had a user management page which listed all users and showed whether they were activated or not. The following code is what we used to ensure that modifications to the first page of objects wouldn’t affect all the other pages.

index.rhtml

<% @users.each do |user| %>
  <%= hidden_field_tag('seen[]', user.id) -%>
  <%= check_box_tag 'activated[]', user.id -%>
<% end %>

role_controller.rb

def index
  if request.post?
    activated_ids = params[:activated].collect {|id| id.to_i} if params[:activated]
    seen_ids = params[:seen].collect {|id| id.to_i} if params[:seen]

    if activated_ids
      seen_ids.each do |id|
        r = User.find_by_id(id)
        r.activated = activated_ids.include?(id)
        r.save
      end
    end
  end
end
August 25, 2008 - (>= v2.1.0)
6 thanks

Rake tasks for gem dependencies

You can manage installation and other tasks for these dependencies with rake tasks, for example:

rake gems:install              # Installs all required gems for this application
rake gems:unpack               # Unpacks the specified gem into vendor/gems

To get all rake tasks about gems:

rake -T gems
August 25, 2008 - (v2.1.0)
4 thanks

Disable default date

If you want a date selector that initially doesn’t have a date selected you can pass it the option :include_blank.

date_select("project", "due_date", :include_blank => true)
August 25, 2008
5 thanks

%w(true false) != [true, false]

Don´t confuse the right:

validates_inclusion_of :published, :in => [true, false]

with the wrong:

validates_inclusion_of :published, :in => %w(true false)

cause:

%w(true false) == ["true", "false"]
August 23, 2008
3 thanks

Include two level has many model example

class Issue < ActiveRecord::Base

  has_many :journals
end

class Journal < ActiveRecord::Base
  belongs_to :issue
  has_many :details, :class_name => "JournalDetail", :dependent => :delete_all
end

class JournalDetail < ActiveRecord::Base
  belongs_to :journal
end

<hr/>

issue = Issue.find(:first, :include => {:journals => :details}

log record follow:

SELECT * FROM `issues` LIMIT 1
SELECT `journals`.* FROM `journals` WHERE (`journals`.`journalized_id` IN (1) and `journals`.`journalized_type` = 'Issue' AND (dustbin <> 1))
SELECT `journal_details`.* FROM `journal_details` WHERE (`journal_details`.journal_id IN (1,2,876177898,935815637))

when execute follow code, then not build sql sentent:

issue.journals
issue.journals[0].details
August 22, 2008
4 thanks

Doesn't add an index

Typically you will want to have an index on foreign keys but this method doesn’t assume that. Outside of the create_table block you should follow this with add_index :

add_index :table_name, :goat_id
# and, if polymorphic:
add_index :table_name, :goat_type
August 22, 2008 - (>= v2.1.0)
13 thanks

Specifying :include no longer necessarily joins the association

Before Rails 2.1, adding an :include=>[:association] in your find method caused ActiveRecord to generate SQL using a join. Since 2.1, it MAY NOT execute as a join.

The join executes a large query and returned potentially duplicate records for a one-to-many association. After 2.1, the query is broken down and eager-loaded using an additional query per association, passing the set of id’s to load, and avoiding the duplicate rows.

The new method eliminates duplicates, but can incur more database overhead. If you are loading a very large set of records (more than a “page”), you may need to “force” the join or use find_by_sql instead.

When you specify a “table.column” syntax within a

:conditions=>["child.name=?", name]  

or

:order=>'child.name'

then ActiveRecord will build the older, full query with the join because you are referencing columns from another table to build. This will cause the duplicate rows to reappear.

Whenever you reference a column from another table in a condition or order clause, ALWAYS use the table name to prefix the column, even if it not ambiguous among the tables involved. Otherwise the query will not be executed as a join and you will receive an SQL error referencing the “missing” column.

You can “force” a join by adding a reference to the other tables in your :conditions or :options parameters, even if the test or sort is irrelevant.

August 20, 2008
5 thanks

Iterate and join blocks

Following LacKac’s idea, we can write render_join (useful to render a collection with a small chunks of code, where a render :partial + :spacer_template would be overkill):

def render_join(collection, join_string, &block)
  output = collection.collect do |item| 
    capture(item, &block)
  end.join(join_string)
  concat(output, block.binding)
end

An example of use:

<% render_join(@items, '<br />') do |item| %>
   <p>Item title: <%= item.title %></p>
<% end %>
August 20, 2008
3 thanks

Current Database Name

The MySQL database adapter extends this and allows you to call

ActiveRecord::Base.connection.current_database

to get the current databases name. Useful when you are actively changing the database you are connected to and sometimes need to check the current one.

http://apidock.com/rails/ActiveRecord/ConnectionAdapters/MysqlAdapter/current_database

August 19, 2008 - (v2.1.0)
8 thanks

preload_associations manually

Usually you preload associations using :include => [ ... ]. In Rails 2.1 each association is fetched with a separate query. Something like:

Post.find(:all, :include => [:tags, :user])

will produce 3 queries - each for posts, tags and users.


But sometimes you have a complex query, which uses :joins => :other_association and conditions between multiple tables, but not the ones you need to include. Then everything is mixed back in one query like in old versions of Rails.

Another case may be when it is not possible to use :include at all, for example while using find_by_sql, but you still want/need to preload associated records.

In rails 2.1 find uses preload_associations internally, when it is possible (There are no joins or conditions between tables).

So then you can preload asociations manually from within your model:

class Post < ActiveRecord::Base

has_many :tags
belongs_to :user
...

def self.find_complex_with_includes
  posts = find_by_sql(...) # or find(:all, :joins => .....)
  preload_associations(posts, [:tags, :user])
  posts
end

end

and then do

@posts = Post.find_complex_with_includes

August 19, 2008 - (v2.1.0)
6 thanks

Namespace or modules in routes

If you have grouped controllers into a module, e.g. admin then you can specify this in the routes using the namespace method:

map.namespace :admin do |admin|
  admin.resources :categories
end

which will map the categories resource giving urls like

/admin/categories/

/admin/categories/new

It will also generate the named routes such as new_admin_category_url and admin_category_path

August 19, 2008
6 thanks

script/generate syntax

To add a post_id field to a comments table, run this:

script\generate migration add_post_id_to_comment post_id:integer

See that it´s not the table name(plural), but the model name(singular),<br /> and post_id:references, does not works like in create_table.

This is the generated migration:

class AddPostIdToComment < ActiveRecord::Migration
 def self.up
   add_column :comments, :post_id, :integer
 end

 def self.down
   remove_column :comments, :post_id
 end
end