The following outlines some of the most commonly used helpers available in Action View. It serves as a good starting point, but reviewing the full API Documentation is also recommended, as it covers all of the helpers in more detail.
1 Formatting
1.1 Dates
These helpers facilitate the display of date and/or time elements as contextual human readable forms.
1.1.1 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.current, 15.seconds.from_now)
# => less than a minute
distance_of_time_in_words(Time.current, 15.seconds.from_now, include_seconds: true)
# => less than 20 seconds
We use Time.current instead of Time.now because it returns the current
time based on the timezone set in Rails, whereas Time.now returns a Time
object based on the server's timezone.
See the distance_of_time_in_words API
Documentation
for more information.
1.1.2 time_ago_in_words
Reports the approximate distance in time between a Time or Date object, or
integer as seconds, and Time.current.
time_ago_in_words(3.minutes.from_now) # => 3 minutes
See the time_ago_in_words API
Documentation
for more information.
1.2 Numbers
A set of methods for converting numbers into formatted strings. Methods are provided for phone numbers, currency, percentage, precision, positional notation, and file size.
1.2.1 number_to_currency
Formats a number into a currency string (e.g., $13.65).
number_to_currency(1234567890.50) # => $1,234,567,890.50
See the number_to_currency API
Documentation
for more information.
1.2.2 number_to_human
Pretty prints (formats and approximates) a number so it is more readable by users; useful for numbers that can get very large.
number_to_human(1234) # => 1.23 Thousand
number_to_human(1234567) # => 1.23 Million
See the number_to_human API
Documentation
for more information.
1.2.3 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) # => 1.21 KB
number_to_human_size(1234567) # => 1.18 MB
See the number_to_human_size API
Documentation
for more information.
1.2.4 number_to_percentage
Formats a number as a percentage string.
number_to_percentage(100, precision: 0) # => 100%
See the number_to_percentage API
Documentation
for more information.
1.2.5 number_to_phone
Formats a number into a phone number (US by default).
number_to_phone(1235551234) # => 123-555-1234
See the number_to_phone API
Documentation
for more information.
1.2.6 number_with_delimiter
Formats a number with grouped thousands using a delimiter.
number_with_delimiter(12345678) # => 12,345,678
See the number_with_delimiter API
Documentation
for more information.
1.2.7 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
See the number_with_precision API
Documentation
for more information.
1.3 Text
A set of methods for filtering, formatting and transforming strings.
1.3.1 excerpt
Given a text and a phrase, excerpt searches for and extracts the first
occurrence of the phrase, plus the requested surrounding text determined by a
radius. An omission marker is prepended/appended if the start/end of the
result does not coincide with the start/end of the text.
excerpt("This is a very beautiful morning", "very", separator: " ", radius: 1)
# => ...a very beautiful...
excerpt("This is also an example", "an", radius: 8, omission: "<chop> ")
#=> <chop> is also an example
See the excerpt API
Documentation
for more information.
1.3.2 pluralize
Returns the singular or plural form of a word based on the value of a number.
pluralize(1, "person") # => 1 person
pluralize(2, "person") # => 2 people
pluralize(3, "person", plural: "users") # => 3 users
See the pluralize API
Documentation
for more information.
1.3.3 truncate
Truncates a given text to a given length. If the text is truncated, an
omission marker will be appended to the result for a total length not exceeding
length.
truncate("Once upon a time in a world far far away")
# => "Once upon a time in a world..."
truncate("Once upon a time in a world far far away", length: 17)
# => "Once upon a ti..."
truncate("one-two-three-four-five", length: 20, separator: "-")
# => "one-two-three..."
truncate("And they found that many people were sleeping better.", length: 25, omission: "... (continued)")
# => "And they f... (continued)"
truncate("<p>Once upon a time in a world far far away</p>", escape: false)
# => "<p>Once upon a time in a wo..."
See the truncate API
Documentation
for more information.
1.3.4 word_wrap
Wraps the text into lines no longer than line_width width.
word_wrap("Once upon a time", line_width: 8)
# => "Once\nupon a\ntime"
See the word_wrap API
Documentation
for more information.
2 Forms
Form helpers simplify working with models compared to using standard HTML elements alone. They offer a range of methods tailored to generating forms based on your models. Some methods correspond to a specific type of input, such as text fields, password fields, select dropdowns, and more. When a form is submitted, the inputs within the form are grouped into the params object and sent back to the controller.
You can learn more about form helpers in the Action View Form Helpers Guide.
3 Navigation
A set of methods to build links and URLs that depend on the routing subsystem.
3.1 button_to
Generates a form that submits to the passed URL. The form has a submit button
with the value of the name.
<%= button_to "Sign in", sign_in_path %>
would output the following HTML:
<form method="post" action="/sessions" class="button_to">
<input type="submit" value="Sign in" />
</form>
See the button_to API
Documentation
for more information.
3.2 current_page?
Returns true if the current request URL matches the given options.
<% if current_page?(controller: 'profiles', action: 'show') %>
<strong>Currently on the profile page</strong>
<% end %>
See the current_page? API
Documentation
for more information.
3.3 link_to
Links to a URL derived from url_for under the hood. It's commonly used to
create links for RESTful resources, especially when passing models as arguments
to link_to.
link_to "Profile", @profile
# => <a href="/profiles/1">Profile</a>
link_to "Book", @book # given a composite primary key [:author_id, :id]
# => <a href="/books/2_1">Book</a>
link_to "Profiles", profiles_path
# => <a href="/profiles">Profiles</a>
link_to nil, "https://example.com"
# => <a href="https://example.com">https://example.com</a>
link_to "Articles", articles_path, id: "articles", class: "article__container"
# => <a href="/articles" class="article__container" id="articles">Articles</a>
You can use a block if your link target can't fit in the name parameter.
<%= link_to @profile do %>
<strong><%= @profile.name %></strong> -- <span>Check it out!</span>
<% end %>
It would output the following HTML:
<a href="/profiles/1">
<strong>David</strong> -- <span>Check it out!</span>
</a>
See the link_to API
Documentation
for more information.
3.4 mail_to
Generates a mailto link tag to the specified email address. You can also
specify the link text, additional HTML options, and whether to encode the email
address.
mail_to "john_doe@gmail.com"
# => <a href="mailto:john_doe@gmail.com">john_doe@gmail.com</a>
mail_to "me@john_doe.com", cc: "me@jane_doe.com",
subject: "This is an example email"
# => <a href="mailto:"me@john_doe.com?cc=me@jane_doe.com&subject=This%20is%20an%20example%20email">"me@john_doe.com</a>
See the mail_to API
Documentation
for more information.
3.5 url_for
Returns the URL for the set of options provided.
url_for @profile
# => /profiles/1
url_for [ @hotel, @booking, page: 2, line: 3 ]
# => /hotels/1/bookings/1?line=3&page=2
url_for @post # given a composite primary key [:blog_id, :id]
# => /posts/1_2
4 Sanitization
A set of methods for scrubbing text of undesired HTML elements. The helpers are particularly useful for helping to ensure that only safe and valid HTML/CSS is rendered. It can also be useful to prevent XSS attacks by escaping or removing potentially malicious content from user input before rendering it in your views.
This functionality is powered internally by the rails-html-sanitizer gem.
4.1 sanitize
The sanitize method 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:
# config/application.rb
class Application < Rails::Application
config.action_view.sanitized_allowed_tags = %w(table tr td)
end
See the sanitize API
Documentation
for more information.
4.2 sanitize_css
Sanitizes a block of CSS code, particularly when it comes across a style
attribute in HTML content. sanitize_css is particularly useful when dealing
with user-generated content or dynamic content that includes style attributes.
The sanitize_css method below will remove the styles that are not allowed.
sanitize_css("background-color: red; color: white; font-size: 16px;")
See the sanitize_css API
Documentation
for more information.
4.3 strip_links
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.
See the strip_links API
Documentation
for more information.
4.4 strip_tags
Strips all HTML tags from the HTML, including comments and special characters.
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
strip_links('<<a href="https://example.org">malformed & link</a>')
# => <malformed & link
See the strip_tags API
Documentation
for more information.
5 Assets
A set of 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.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.asset_host = "assets.example.com"
then the corresponding URL for an image_tag would be:
image_tag("rails.png")
# => <img src="//assets.example.com/images/rails.png" />
5.1 audio_tag
Generates an HTML audio tag with source(s), either as a single tag for a string
source or nested source tags within an array for multiple sources. The sources
can be full paths, files in your public audios directory, or Active Storage
attachments.
audio_tag("sound")
# => <audio src="/audios/sound"></audio>
audio_tag("sound.wav", "sound.mid")
# => <audio><source src="/audios/sound.wav" /><source src="/audios/sound.mid" /></audio>
audio_tag("sound", controls: true)
# => <audio controls="controls" src="/audios/sound"></audio>
Internally, audio_tag uses audio_path from the
AssetUrlHelpers
to build the audio path.
See the audio_tag API
Documentation
for more information.
5.2 auto_discovery_link_tag
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" />
See the auto_discovery_link_tag API
Documentation
for more information.
5.3 favicon_link_tag
Returns a link tag for a favicon managed by the asset pipeline. The source can
be a full path or a file that exists in your assets directory.
favicon_link_tag
# => <link href="/assets/favicon.ico" rel="icon" type="image/x-icon" />
See the favicon_link_tag API
Documentation
for more information.
5.4 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" />
image_tag("icon.png", size: "16x10", alt: "Edit Article")
# => <img src="/assets/icon.png" width="16" height="10" alt="Edit Article" />
Internally, image_tag uses image_path from the
AssetUrlHelpers
to build the image path.
See the image_tag API
Documentation
for more information.
5.5 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>
javascript_include_tag("common", async: true)
# => <script src="/assets/common.js" async="async"></script>
Some of the most common attributes are async and defer, where async will
allow the script to be loaded in parallel to be parsed and evaluated as soon as
possible, and defer will indicate that the script is meant to be executed
after the document has been parsed.
Internally, javascript_include_tag uses javascript_path from the
AssetUrlHelpers
to build the script path.
See the javascript_include_tag API
Documentation
for more information.
5.6 picture_tag
Returns an HTML picture tag for the source. It supports passing a String, an Array, or a Block.
picture_tag("icon.webp", "icon.png")
This generates the following HTML:
<picture>
<source srcset="/assets/icon.webp" type="image/webp" />
<source srcset="/assets/icon.png" type="image/png" />
<img src="/assets/icon.png" />
</picture>
See the picture_tag API
Documentation
for more information.
5.7 preload_link_tag
Returns a link tag that browsers can use to preload the source. The source can be the path of a resource managed by the asset pipeline, a full path, or a URI.
preload_link_tag("application.css")
# => <link rel="preload" href="/assets/application.css" as="style" type="text/css" />
See the preload_link_tag API
Documentation
for more information.
5.8 stylesheet_link_tag
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" rel="stylesheet" />
stylesheet_link_tag("application", media: "all")
# => <link href="/assets/application.css" media="all" rel="stylesheet" />
media is used to specify the media type for the link. The most common media
types are all, screen, print, and speech.
Internally, stylesheet_link_tag uses stylesheet_path from the
AssetUrlHelpers
to build the stylesheet path.
See the stylesheet_link_tag API
Documentation
for more information.
5.9 video_tag
Generate an HTML video tag with source(s), either as a single tag for a string
source or nested source tags within an array for multiple sources. The sources
can be full paths, files in your public videos directory, or Active Storage
attachments.
video_tag("trailer")
# => <video src="/videos/trailer"></video>
video_tag(["trailer.ogg", "trailer.flv"])
# => <video><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>
video_tag("trailer", controls: true)
# => <video controls="controls" src="/videos/trailer"></video>
Internally, video_tag uses video_path from the
AssetUrlHelpers
to build the video path.
See the video_tag API
Documentation
for more information.
6 JavaScript
A set of methods for working with JavaScript in your views.
6.1 escape_javascript
Escapes carriage returns and single and double quotes for JavaScript segments. You would use this method to take a string of text and make sure that it doesn’t contain any invalid characters when the browser tries to parse it.
For example, if you have a partial with a greeting that contains double quotes, you can escape the greeting to use in a JavaScript alert.
<%# app/views/users/greeting.html.erb %>
My name is <%= current_user.name %>, and I'm here to say "Welcome to our website!"
<script>
var greeting = "<%= escape_javascript render('users/greeting') %>";
alert(`Hello, ${greeting}`);
</script>
This will escape the quotes correctly and display the greeting in an alert box.
See the escape_javascript API
Documentation
for more information.
6.2 javascript_tag
Returns a JavaScript tag wrapping the provided code. You can pass a hash of
options to control the behavior of the <script> tag.
javascript_tag("alert('All is good')", type: "application/javascript")
<script type="application/javascript">
//<![CDATA[
alert('All is good')
//]]>
</script>
Instead of passing the content as an argument, you can also use a block.
<%= javascript_tag type: "application/javascript" do %>
alert("Welcome to my app!")
<% end %>
See the javascript_tag API
Documentation
for more information.
7 Alternative Tags
A set of methods to generate HTML tags programmatically.
7.1 tag
Generates a standalone HTML tag with the given name and options.
Every tag can be built with:
tag.some_tag_name(optional content, options)
where tag name can be e.g. br, div, section, article, or any tag really.
For example, here are some common uses:
tag.h1 "All titles fit to print"
# => <h1>All titles fit to print</h1>
tag.div "Hello, world!"
# => <div>Hello, world!</div>
Additionally, you can pass options to add attributes to the generated tag.
tag.section class: %w( kitties puppies )
# => <section class="kitties puppies"></section>
In addition, HTML data-* attributes can be passed to the tag helper using
the data option, with a hash containing key-value pairs of sub-attributes. The
sub-attributes are then converted to data-* attributes that are dasherized in
order to work well with JavaScript.
tag.div data: { user_id: 123 }
# => <div data-user-id="123"></div>
See the tag API
Documentation
for more information.
7.2 token_list
Returns a string of tokens built from the arguments provided. This method is
also aliased as class_names.
token_list("cats", "dogs")
# => "cats dogs"
token_list(nil, false, 123, "", "foo", { bar: true })
# => "123 foo bar"
mobile, alignment = true, "center"
token_list("flex items-#{alignment}", "flex-col": mobile)
# => "flex items-center flex-col"
class_names("flex items-#{alignment}", "flex-col": mobile) # using the alias
# => "flex items-center flex-col"
8 Capture Blocks
A set of methods to let you extract generated markup which can be used in other parts of a template or layout file.
It provides a method to capture blocks into variables through capture, and a
way to capture a block of markup for use in a layout through content_for.
8.1 capture
The capture method allows you to extract part of a template into a variable.
<% @greeting = capture do %>
<p>Welcome! The date and time is <%= Time.current %></p>
<% end %>
You can then use this variable anywhere in your templates, layouts, or helpers.
<html>
<head>
<title>Welcome!</title>
</head>
<body>
<%= @greeting %>
</body>
</html>