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Action View Helpers

After reading this guide, you will know:

1 Overview of helpers provided by Action View

WIP: Not all the helpers are listed here. For a full list see the API documentation

The following is only a brief overview summary of the helpers available in Action View. It's recommended that you review the API Documentation, which covers all of the helpers in more detail, but this should serve as a good starting point.

1.1 AssetTagHelper

This module provides methods for generating HTML that links views to assets such as images, JavaScript files, stylesheets, and feeds.

By default, Rails links to these assets on the current host in the public folder, but you can direct Rails to link to assets from a dedicated assets server by setting config.action_controller.asset_host in the application configuration, typically in config/environments/production.rb. For example, let's say your asset host is assets.example.com:

config.action_controller.asset_host = "assets.example.com"
image_tag("rails.png") 
# => <img src="http://assets.example.com/images/rails.png" />

Returns a link tag that browsers and feed readers can use to auto-detect an RSS, Atom, or JSON feed.

auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", { title: "RSS Feed" }) 
# => <link rel="alternate" type="application/rss+xml" title="RSS Feed" href="http://www.example.com/feed.rss" />
1.1.2 image_path

Computes the path to an image asset in the app/assets/images directory. Full paths from the document root will be passed through. Used internally by image_tag to build the image path.

image_path("edit.png") # => /assets/edit.png

Fingerprint will be added to the filename if config.assets.digest is set to true.

image_path("edit.png") 
# => /assets/edit-2d1a2db63fc738690021fedb5a65b68e.png
1.1.3 image_url

Computes the URL to an image asset in the app/assets/images directory. This will call image_path internally and merge with your current host or your asset host.

image_url("edit.png") # => http://www.example.com/assets/edit.png
1.1.4 image_tag

Returns an HTML image tag for the source. The source can be a full path or a file that exists in your app/assets/images directory.

image_tag("icon.png") # => <img src="/assets/icon.png" />
1.1.5 javascript_include_tag

Returns an HTML script tag for each of the sources provided. You can pass in the filename (.js extension is optional) of JavaScript files that exist in your app/assets/javascripts directory for inclusion into the current page or you can pass the full path relative to your document root.

javascript_include_tag "common" 
# => <script src="/assets/common.js"></script>
1.1.6 javascript_path

Computes the path to a JavaScript asset in the app/assets/javascripts directory. If the source filename has no extension, .js will be appended. Full paths from the document root will be passed through. Used internally by javascript_include_tag to build the script path.

javascript_path "common" # => /assets/common.js
1.1.7 javascript_url

Computes the URL to a JavaScript asset in the app/assets/javascripts directory. This will call javascript_path internally and merge with your current host or your asset host.

javascript_url "common" 
# => http://www.example.com/assets/common.js

Returns a stylesheet link tag for the sources specified as arguments. If you don't specify an extension, .css will be appended automatically.

stylesheet_link_tag "application" 
# => <link href="/assets/application.css" media="screen" rel="stylesheet" />
1.1.9 stylesheet_path

Computes the path to a stylesheet asset in the app/assets/stylesheets directory. If the source filename has no extension, .css will be appended. Full paths from the document root will be passed through. Used internally by stylesheet_link_tag to build the stylesheet path.

stylesheet_path "application" # => /assets/application.css
1.1.10 stylesheet_url

Computes the URL to a stylesheet asset in the app/assets/stylesheets directory. This will call stylesheet_path internally and merge with your current host or your asset host.

stylesheet_url "application" 
# => http://www.example.com/assets/application.css

1.2 AtomFeedHelper

1.2.1 atom_feed

This helper makes building an Atom feed easy. Here's a full usage example:

config/routes.rb

resources :articles

app/controllers/articles_controller.rb

def index
  @articles = Article.all

  respond_to do |format|
    format.html
    format.atom
  end
end

app/views/articles/index.atom.builder

atom_feed do |feed|
  feed.title("Articles Index")
  feed.updated(@articles.first.created_at)

  @articles.each do |article|
    feed.entry(article) do |entry|
      entry.title(article.title)
      entry.content(article.body, type: 'html')

      entry.author do |author|
        author.name(article.author_name)
      end
    end
  end
end

1.3 BenchmarkHelper

1.3.1 benchmark

Allows you to measure the execution time of a block in a template and records the result to the log. Wrap this block around expensive operations or possible bottlenecks to get a time reading for the operation.

<% benchmark "Process data files" do %>
  <%= expensive_files_operation %>
<% end %>

This would add something like "Process data files (0.34523)" to the log, which you can then use to compare timings when optimizing your code.

1.4 CacheHelper

1.4.1 cache

A method for caching fragments of a view rather than an entire action or page. This technique is useful for caching pieces like menus, lists of news topics, static HTML fragments, and so on. This method takes a block that contains the content you wish to cache. See AbstractController::Caching::Fragments for more information.

<% cache do %>
  <%= render "shared/footer" %>
<% end %>

1.5 CaptureHelper

1.5.1 capture

The capture method allows you to extract part of a template into a variable. You can then use this variable anywhere in your templates or layout.

<% @greeting = capture do %>
  <p>Welcome! The date and time is <%= Time.now %></p>
<% end %>

The captured variable can then be used anywhere else.

<html>
  <head>
    <title>Welcome!</title>
  </head>
  <body>
    <%= @greeting %>
  </body>
</html>
1.5.2 content_for

Calling content_for stores a block of markup in an identifier for later use. You can make subsequent calls to the stored content in other templates or the layout by passing the identifier as an argument to yield.

For example, let's say we have a standard application layout, but also a special page that requires certain JavaScript that the rest of the site doesn't need. We can use content_for to include this JavaScript on our special page without fattening up the rest of the site.

app/views/layouts/application.html.erb

<html>
  <head>
    <title>Welcome!</title>
    <%= yield :special_script %>
  </head>
  <body>
    <p>Welcome! The date and time is <%= Time.now %></p>
  </body>
</html>

app/views/articles/special.html.erb

<p>This is a special page.</p>

<% content_for :special_script do %>
  <script>alert('Hello!')</script>
<% end %>

1.6 DateHelper

1.6.1 date_select

Returns a set of select tags (one for year, month, and day) pre-selected for accessing a specified date-based attribute.

date_select("article", "published_on")
1.6.2 datetime_select

Returns a set of select tags (one for year, month, day, hour, and minute) pre-selected for accessing a specified datetime-based attribute.

datetime_select("article", "published_on")
1.6.3 distance_of_time_in_words

Reports the approximate distance in time between two Time or Date objects or integers as seconds. Set include_seconds to true if you want more detailed approximations.

distance_of_time_in_words(Time.now, Time.now + 15.seconds) 
# => less than a minute
distance_of_time_in_words(Time.now, Time.now + 15.seconds, include_seconds: true) 
# => less than 20 seconds
1.6.4 select_date

Returns a set of HTML select-tags (one for year, month, and day) pre-selected with the date provided.

# Generates a date select that defaults to the date provided (six days after today)
select_date(Time.today + 6.days)

# Generates a date select that defaults to today (no specified date)
select_date()
1.6.5 select_datetime

Returns a set of HTML select-tags (one for year, month, day, hour, and minute) pre-selected with the datetime provided.

# Generates a datetime select that defaults to the datetime provided (four days after today)
select_datetime(Time.now + 4.days)

# Generates a datetime select that defaults to today (no specified datetime)
select_datetime()
1.6.6 select_day

Returns a select tag with options for each of the days 1 through 31 with the current day selected.

# Generates a select field for days that defaults to the day for the date provided
select_day(Time.today + 2.days)

# Generates a select field for days that defaults to the number given
select_day(5)
1.6.7 select_hour

Returns a select tag with options for each of the hours 0 through 23 with the current hour selected.

# Generates a select field for hours that defaults to the hours for the time provided
select_hour(Time.now + 6.hours)
1.6.8 select_minute

Returns a select tag with options for each of the minutes 0 through 59 with the current minute selected.

# Generates a select field for minutes that defaults to the minutes for the time provided.
select_minute(Time.now + 10.minutes)
1.6.9 select_month

Returns a select tag with options for each of the months January through December with the current month selected.

# Generates a select field for months that defaults to the current month
select_month(Date.today)
1.6.10 select_second

Returns a select tag with options for each of the seconds 0 through 59 with the current second selected.

# Generates a select field for seconds that defaults to the seconds for the time provided
select_second(Time.now + 16.seconds)
1.6.11 select_time

Returns a set of HTML select-tags (one for hour and minute).

# Generates a time select that defaults to the time provided
select_time(Time.now)
1.6.12 select_year

Returns a select tag with options for each of the five years on each side of the current, which is selected. The five year radius can be changed using the :start_year and :end_year keys in the options.

# Generates a select field for five years on either side of Date.today that defaults to the current year
select_year(Date.today)

# Generates a select field from 1900 to 2009 that defaults to the current year
select_year(Date.today, start_year: 1900, end_year: 2009)
1.6.13 time_ago_in_words

Like distance_of_time_in_words, but where to_time is fixed to Time.now.

time_ago_in_words(3.minutes.from_now) # => 3 minutes
1.6.14 time_select

Returns a set of select tags (one for hour, minute, and optionally second) pre-selected for accessing a specified time-based attribute. The selects are prepared for multi-parameter assignment to an Active Record object.

# Creates a time select tag that, when POSTed, will be stored in the order variable in the submitted attribute
time_select("order", "submitted")

1.7 DebugHelper

Returns a pre tag that has object dumped by YAML. This creates a very readable way to inspect an object.

my_hash = { 'first' => 1, 'second' => 'two', 'third' => [1,2,3] }
debug(my_hash)
<pre class='debug_dump'>---
first: 1
second: two
third:
- 1
- 2
- 3
</pre>

1.8 FormHelper

Form helpers are designed to make working with models much easier compared to using just standard HTML elements by providing a set of methods for creating forms based on your models. This helper generates the HTML for forms, providing a method for each sort of input (e.g., text, password, select, and so on). When the form is submitted (i.e., when the user hits the submit button or form.submit is called via JavaScript), the form inputs will be bundled into the params object and passed back to the controller.

There are two types of form helpers: those that specifically work with model attributes and those that don't. This helper deals with those that work with model attributes; to see an example of form helpers that don't work with model attributes, check the ActionView::Helpers::FormTagHelper documentation.

The core method of this helper, form_with, gives you the ability to create a form for a model instance; for example, let's say that you have a model Person and want to create a new instance of it:

<!-- Note: a @person variable will have been created in the controller (e.g. @person = Person.new) -->
<%= form_with model: @person do |form| %>
  <%= form.text_field :first_name %>
  <%= form.text_field :last_name %>
  <%= submit_tag 'Create' %>
<% end %>

The HTML generated for this would be:

<form class="new_person" id="new_person" action="/people" accept-charset="UTF-8" method="post">
  <input name="utf8" type="hidden" value="&#x2713;" />
  <input type="hidden" name="authenticity_token" value="lTuvBzs7ANygT0NFinXj98tfw3Emfm65wwYLbUvoWsK2pngccIQSUorM2C035M9dZswXgWTvKwFS8W5TVblpYw==" />
  <input type="text" name="person[first_name]" id="person_first_name" />
  <input type="text" name="person[last_name]" id="person_last_name" />
  <input type="submit" name="commit" value="Create" data-disable-with="Create" />
</form>

The params object created when this form is submitted would look like:

{"utf8" => "✓", "authenticity_token" => "lTuvBzs7ANygT0NFinXj98tfw3Emfm65wwYLbUvoWsK2pngccIQSUorM2C035M9dZswXgWTvKwFS8W5TVblpYw==", "person" => {"first_name" => "William", "last_name" => "Smith"}, "commit" => "Create", "controller" => "people", "action" => "create"}

The params hash has a nested person value, which can therefore be accessed with params[:person] in the controller.

1.8.1 check_box

Returns a checkbox tag tailored for accessing a specified attribute.

# Let's say that @article.validated? is 1:
check_box("article", "validated")
# => <input type="checkbox" id="article_validated" name="article[validated]" value="1" />
#    <input name="article[validated]" type="hidden" value="0" />
1.8.2 fields_for

Creates a scope around a specific model object. This makes fields_for suitable for specifying additional model objects in the same form:

<%= form_with model: @person do |person_form| %>
  First name: <%= person_form.text_field :first_name %>
  Last name : <%= person_form.text_field :last_name %>

  <%= fields_for @person.permission do |permission_fields| %>
    Admin?  : <%= permission_fields.check_box :admin %>
  <% end %>
<% end %>
1.8.3 file_field

Returns a file upload input tag tailored for accessing a specified attribute.

file_field(:user, :avatar)
# => <input type="file" id="user_avatar" name="user[avatar]" />
1.8.4 form_with

Creates a form builder to work with. If a model argument is specified, form fields will be scoped to that model, and form field values will be prepopulated with corresponding model attributes.

<%= form_with model: @article do |form| %>
  <%= form.label :title, 'Title' %>:
  <%= form.text_field :title %><br>
  <%= form.label :body, 'Body' %>:
  <%= form.text_area :body %><br>
<% end %>
1.8.5 hidden_field

Returns a hidden input tag tailored for accessing a specified attribute.

hidden_field(:user, :token)
# => <input type="hidden" id="user_token" name="user[token]" value="#{@user.token}" />
1.8.6 label

Returns a label tag tailored for labelling an input field for a specified attribute.

label(:article, :title)
# => <label for="article_title">Title</label>
1.8.7 password_field

Returns an input tag of the "password" type tailored for accessing a specified attribute.

password_field(:login, :pass)
# => <input type="text" id="login_pass" name="login[pass]" value="#{@login.pass}" />
1.8.8 radio_button

Returns a radio button tag for accessing a specified attribute.

# Let's say that @article.category returns "rails":
radio_button("article", "category", "rails")
radio_button("article", "category", "java")
# => <input type="radio" id="article_category_rails" name="article[category]" value="rails" checked="checked" />
#    <input type="radio" id="article_category_java" name="article[category]" value="java" />
1.8.9 text_area

Returns a textarea opening and closing tag set tailored for accessing a specified attribute.

text_area(:comment, :text, size: "20x30")
# => <textarea cols="20" rows="30" id="comment_text" name="comment[text]">
#      #{@comment.text}
#    </textarea>
1.8.10 text_field

Returns an input tag of the "text" type tailored for accessing a specified attribute.

text_field(:article, :title)
# => <input type="text" id="article_title" name="article[title]" value="#{@article.title}" />
1.8.11 email_field

Returns an input tag of the "email" type tailored for accessing a specified attribute.

email_field(:user, :email)
# => <input type="email" id="user_email" name="user[email]" value="#{@user.email}" />
1.8.12 url_field

Returns an input tag of the "url" type tailored for accessing a specified attribute.

url_field(:user, :url)
# => <input type="url" id="user_url" name="user[url]" value="#{@user.url}" />

1.9 FormOptionsHelper

Provides a number of methods for turning different kinds of containers into a set of option tags.

1.9.1 collection_select

Returns select and option tags for the collection of existing return values of method for object's class.

Example object structure for use with this method:

class Article < ApplicationRecord
  belongs_to :author
end

class Author < ApplicationRecord
  has_many :articles
  def name_with_initial
    "#{first_name.first}. #{last_name}"
  end
end

Sample usage (selecting the associated Author for an instance of Article, @article):

collection_select(:article, :author_id, Author.all, :id, :name_with_initial, { prompt: true })

If @article.author_id is 1, this would return:

<select name="article[author_id]">
  <option value="">Please select</option>
  <option value="1" selected="selected">D. Heinemeier Hansson</option>
  <option value="2">D. Thomas</option>
  <option value="3">M. Clark</option>
</select>
1.9.2 collection_radio_buttons

Returns radio_button tags for the collection of existing return values of method for object's class.

Example object structure for use with this method:

class Article < ApplicationRecord
  belongs_to :author
end

class Author < ApplicationRecord
  has_many :articles
  def name_with_initial
    "#{first_name.first}. #{last_name}"
  end
end

Sample usage (selecting the associated Author for an instance of Article, @article):

collection_radio_buttons(:article, :author_id, Author.all, :id, :name_with_initial)

If @article.author_id is 1, this would return:

<input id="article_author_id_1" name="article[author_id]" type="radio" value="1" checked="checked" />
<label for="article_author_id_1">D. Heinemeier Hansson</label>
<input id="article_author_id_2" name="article[author_id]" type="radio" value="2" />
<label for="article_author_id_2">D. Thomas</label>
<input id="article_author_id_3" name="article[author_id]" type="radio" value="3" />
<label for="article_author_id_3">M. Clark</label>

Recovering some option passed (e.g. programmatically checking an object from collection):

collection_radio_buttons(:article, :author_id, Author.all, :id, :name_with_initial, {checked: Author.last})

In this case, the last object from the collection will be checked:

<input id="article_author_id_1" name="article[author_id]" type="radio" value="1" />
<label for="article_author_id_1">D. Heinemeier Hansson</label>
<input id="article_author_id_2" name="article[author_id]" type="radio" value="2" />
<label for="article_author_id_2">D. Thomas</label>
<input id="article_author_id_3" name="article[author_id]" type="radio" value="3" checked="checked" />
<label for="article_author_id_3">M. Clark</label>

To access the passed options programmatically (e.g. adding a custom class if checked):

Sample html.erb

<%= collection_radio_buttons(:article, :author_id, Author.all, :id, :name_with_initial, {checked: Author.last, required: true} do |rb| %>
      <%= rb.label(class: "#{'my-custom-class' if rb.value == Author.last.id}") { rb.radio_button + rb.text } %>
<% end %>
1.9.3 collection_check_boxes

Returns check_box tags for the collection of existing return values of method for object's class.

Example object structure for use with this method:

class Article < ApplicationRecord
  has_and_belongs_to_many :authors
end

class Author < ApplicationRecord
  has_and_belongs_to_many :articles
  def name_with_initial
    "#{first_name.first}. #{last_name}"
  end
end

Sample usage (selecting the associated Authors for an instance of Article, @article):

collection_check_boxes(:article, :author_ids, Author.all, :id, :name_with_initial)

If @article.author_ids is [1], this would return:

<input id="article_author_ids_1" name="article[author_ids][]" type="checkbox" value="1" checked="checked" />
<label for="article_author_ids_1">D. Heinemeier Hansson</label>
<input id="article_author_ids_2" name="article[author_ids][]" type="checkbox" value="2" />
<label for="article_author_ids_2">D. Thomas</label>
<input id="article_author_ids_3" name="article[author_ids][]" type="checkbox" value="3" />
<label for="article_author_ids_3">M. Clark</label>
<input name="article[author_ids][]" type="hidden" value="" />
1.9.4 option_groups_from_collection_for_select

Returns a string of option tags, like options_from_collection_for_select, but groups them by optgroup tags based on the object relationships of the arguments.

Example object structure for use with this method:

class Continent < ApplicationRecord
  has_many :countries
  # attribs: id, name
end

class Country < ApplicationRecord
  belongs_to :continent
  # attribs: id, name, continent_id
end

Sample usage:

option_groups_from_collection_for_select(@continents, :countries, :name, :id, :name, 3)

Possible output:

<optgroup label="Africa">
  <option value="1">Egypt</option>
  <option value="4">Rwanda</option>
  ...
</optgroup>
<optgroup label="Asia">
  <option value="3" selected="selected">China</option>
  <option value="12">India</option>
  <option value="5">Japan</option>
  ...
</optgroup>

Only the optgroup and option tags are returned, so you still have to wrap the output in an appropriate select tag.

1.9.5 options_for_select

Accepts a container (hash, array, enumerable, your type) and returns a string of option tags.

options_for_select([ "VISA", "MasterCard" ])
# => <option>VISA</option> <option>MasterCard</option>

Only the option tags are returned, you have to wrap this call in a regular HTML select tag.

1.9.6 options_from_collection_for_select

Returns a string of option tags that have been compiled by iterating over the collection and assigning the result of a call to the value_method as the option value and the text_method as the option text.

options_from_collection_for_select(collection, value_method, text_method, selected = nil)

For example, imagine a loop iterating over each person in @project.people to generate an input tag:

options_from_collection_for_select(@project.people, "id", "name")
# => <option value="#{person.id}">#{person.name}</option>

Only the option tags are returned, you have to wrap this call in a regular HTML select tag.

1.9.7 select

Create a select tag and a series of contained option tags for the provided object and method.

Example:

select("article", "person_id", Person.all.collect { |p| [ p.name, p.id ] }, { include_blank: true })

If @article.person_id is 1, this would become:

<select name="article[person_id]">
  <option value=""></option>
  <option value="1" selected="selected">David</option>
  <option value="2">Eileen</option>
  <option value="3">Rafael</option>
</select>
1.9.8 time_zone_options_for_select

Returns a string of option tags for pretty much any time zone in the world.

1.9.9 time_zone_select

Returns select and option tags for the given object and method, using time_zone_options_for_select to generate the list of option tags.

time_zone_select("user", "time_zone")
1.9.10 date_field

Returns an input tag of the "date" type tailored for accessing a specified attribute.

date_field("user", "dob")

1.10 FormTagHelper

Provides a number of methods for creating form tags that are not scoped to model objects. Instead, you provide the names and values manually.

1.10.1 check_box_tag

Creates a check box form input tag.

check_box_tag 'accept'
# => <input id="accept" name="accept" type="checkbox" value="1" />
1.10.2 field_set_tag

Creates a field set for grouping HTML form elements.

<%= field_set_tag do %>
  <p><%= text_field_tag 'name' %></p>
<% end %>
# => <fieldset><p><input id="name" name="name" type="text" /></p></fieldset>
1.10.3 file_field_tag

Creates a file upload field.

<%= form_with url: new_account_avatar_path(@account), multipart: true do %>
  <label for="file">Avatar:</label> <%= file_field_tag 'avatar' %>
  <%= submit_tag %>
<% end %>

Example output:

file_field_tag 'attachment'
# => <input id="attachment" name="attachment" type="file" />
1.10.4 hidden_field_tag

Creates a hidden form input field used to transmit data that would be lost due to HTTP's statelessness or data that should be hidden from the user.

hidden_field_tag 'token', 'VUBJKB23UIVI1UU1VOBVI@'
# => <input id="token" name="token" type="hidden" value="VUBJKB23UIVI1UU1VOBVI@" />
1.10.5 image_submit_tag

Displays an image which when clicked will submit the form.

image_submit_tag("login.png")
# => <input src="/images/login.png" type="image" />
1.10.6 label_tag

Creates a label field.

label_tag 'name'
# => <label for="name">Name</label>
1.10.7 password_field_tag

Creates a password field, a masked text field that will hide the users input behind a mask character.

password_field_tag 'pass'
# => <input id="pass" name="pass" type="password" />
1.10.8 radio_button_tag

Creates a radio button; use groups of radio buttons named the same to allow users to select from a group of options.

radio_button_tag 'favorite_color', 'maroon'
# => <input id="favorite_color_maroon" name="favorite_color" type="radio" value="maroon" />
1.10.9 select_tag

Creates a dropdown selection box.

select_tag "people", "<option>David</option>"
# => <select id="people" name="people"><option>David</option></select>
1.10.10 submit_tag

Creates a submit button with the text provided as the caption.

submit_tag "Publish this article"
# => <input name="commit" type="submit" value="Publish this article" />
1.10.11 text_area_tag

Creates a text input area; use a textarea for longer text inputs such as blog posts or descriptions.

text_area_tag 'article'
# => <textarea id="article" name="article"></textarea>
1.10.12 text_field_tag

Creates a standard text field; use these text fields to input smaller chunks of text like a username or a search query.

text_field_tag 'name'
# => <input id="name" name="name" type="text" />
1.10.13 email_field_tag

Creates a standard input field of email type.

email_field_tag 'email'
# => <input id="email" name="email" type="email" />
1.10.14 url_field_tag

Creates a standard input field of url type.

url_field_tag 'url'
# => <input id="url" name="url" type="url" />
1.10.15 date_field_tag

Creates a standard input field of date type.

date_field_tag "dob"
# => <input id="dob" name="dob" type="date" />

1.11 JavaScriptHelper

Provides functionality for working with JavaScript in your views.

1.11.1 escape_javascript

Escape carrier returns and single and double quotes for JavaScript segments.

1.11.2 javascript_tag

Returns a JavaScript tag wrapping the provided code.

javascript_tag "alert('All is good')"
<script>
//<![CDATA[
alert('All is good')
//]]>
</script>

1.12 NumberHelper

Provides methods for converting numbers into formatted strings. Methods are provided for phone numbers, currency, percentage, precision, positional notation, and file size.

1.12.1 number_to_currency

Formats a number into a currency string (e.g., $13.65).

number_to_currency(1234567890.50) # => $1,234,567,890.50
1.12.2 number_to_human_size

Formats the bytes in size into a more understandable representation; useful for reporting file sizes to users.

number_to_human_size(1234)    # => 1.2 KB
number_to_human_size(1234567) # => 1.2 MB
1.12.3 number_to_percentage

Formats a number as a percentage string.

number_to_percentage(100, precision: 0) # => 100%
1.12.4 number_to_phone

Formats a number into a phone number (US by default).

number_to_phone(1235551234) # => 123-555-1234
1.12.5 number_with_delimiter

Formats a number with grouped thousands using a delimiter.

number_with_delimiter(12345678) # => 12,345,678
1.12.6 number_with_precision

Formats a number with the specified level of precision, which defaults to 3.

number_with_precision(111.2345)               # => 111.235
number_with_precision(111.2345, precision: 2) # => 111.23

1.13 SanitizeHelper

The SanitizeHelper module provides a set of methods for scrubbing text of undesired HTML elements.

1.13.1 sanitize

This sanitize helper will HTML encode all tags and strip all attributes that aren't specifically allowed.

sanitize @article.body

If either the :attributes or :tags options are passed, only the mentioned attributes and tags are allowed and nothing else.

sanitize @article.body, tags: %w(table tr td), attributes: %w(id class style)

To change defaults for multiple uses, for example adding table tags to the default:

class Application < Rails::Application
  config.action_view.sanitized_allowed_tags = 'table', 'tr', 'td'
end
1.13.2 sanitize_css(style)

Sanitizes a block of CSS code.

Strips all link tags from text leaving just the link text.

strip_links('<a href="https://rubyonrails.org">Ruby on Rails</a>')
# => Ruby on Rails
strip_links('emails to <a href="mailto:me@email.com">me@email.com</a>.')
# => emails to me@email.com.
strip_links('Blog: <a href="http://myblog.com/">Visit</a>.')
# => Blog: Visit.
1.13.4 strip_tags(html)

Strips all HTML tags from the html, including comments. This functionality is powered by the rails-html-sanitizer gem.

strip_tags("Strip <i>these</i> tags!")
# => Strip these tags!
strip_tags("<b>Bold</b> no more!  <a href='more.html'>See more</a>")
# => Bold no more!  See more

NB: The output may still contain unescaped '<', '>', '&' characters and confuse browsers.

1.14 UrlHelper

Provides methods to make links and get URLs that depend on the routing subsystem.

1.14.1 url_for

Returns the URL for the set of options provided.

1.14.1.1 Examples
url_for @profile
# => /profiles/1

url_for [ @hotel, @booking, page: 2, line: 3 ]
# => /hotels/1/bookings/1?line=3&page=2

Links to a URL derived from url_for under the hood. Primarily used to create RESTful resource links, which for this example, boils down to when passing models to link_to.

Examples

link_to "Profile", @profile
# => <a href="/profiles/1">Profile</a>

You can use a block as well if your link target can't fit in the name parameter. ERB example:

<%= link_to @profile do %>
  <strong><%= @profile.name %></strong> -- <span>Check it out!</span>
<% end %>

would output:

<a href="/profiles/1">
  <strong>David</strong> -- <span>Check it out!</span>
</a>

See the API Documentation for more information

1.14.3 button_to

Generates a form that submits to the passed URL. The form has a submit button with the value of the name.

1.14.3.1 Examples
<%= button_to "Sign in", sign_in_path %>

would roughly output something like:

<form method="post" action="/sessions" class="button_to">
  <input type="submit" value="Sign in" />
</form>

See the API Documentation for more information

1.15 CsrfHelper

Returns meta tags "csrf-param" and "csrf-token" with the name of the cross-site request forgery protection parameter and token, respectively.

<%= csrf_meta_tags %>

Regular forms generate hidden fields so they do not use these tags. More details can be found in the Rails Security Guide.

Feedback

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