```
#### auto_discovery_link_tag
Returns a link tag that browsers and feed readers can use to auto-detect an RSS, Atom, or JSON feed.
```ruby
auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", { title: "RSS Feed" })
# =>
```
#### 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.
```ruby
image_path("edit.png") # => /assets/edit.png
```
Fingerprint will be added to the filename if config.assets.digest is set to true.
```ruby
image_path("edit.png")
# => /assets/edit-2d1a2db63fc738690021fedb5a65b68e.png
```
#### 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.
```ruby
image_url("edit.png") # => http://www.example.com/assets/edit.png
```
#### 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.
```ruby
image_tag("icon.png") # => 
```
#### 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.
```ruby
javascript_include_tag "common"
# =>
```
#### 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.
```ruby
javascript_path "common" # => /assets/common.js
```
#### 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.
```ruby
javascript_url "common"
# => http://www.example.com/assets/common.js
```
#### 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.
```ruby
stylesheet_link_tag "application"
# =>
```
#### 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.
```ruby
stylesheet_path "application" # => /assets/application.css
```
#### 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.
```ruby
stylesheet_url "application"
# => http://www.example.com/assets/application.css
```
### AtomFeedHelper
#### atom_feed
This helper makes building an Atom feed easy. Here's a full usage example:
**config/routes.rb**
```ruby
resources :articles
```
**app/controllers/articles_controller.rb**
```ruby
def index
@articles = Article.all
respond_to do |format|
format.html
format.atom
end
end
```
**app/views/articles/index.atom.builder**
```ruby
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
```
### BenchmarkHelper
#### 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.
```html+erb
<% 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.
### CacheHelper
#### 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.
```erb
<% cache do %>
<%= render "shared/footer" %>
<% end %>
```
### CaptureHelper
#### 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.
```html+erb
<% @greeting = capture do %>
Welcome! The date and time is <%= Time.now %>
<% end %> ``` The captured variable can then be used anywhere else. ```html+erbWelcome! The date and time is <%= Time.now %>
``` **app/views/articles/special.html.erb** ```html+erbThis is a special page.
<% content_for :special_script do %> <% end %> ``` ### DateHelper #### 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. ```ruby 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 ``` #### time_ago_in_words Like `distance_of_time_in_words`, but where `to_time` is fixed to `Time.now`. ```ruby time_ago_in_words(3.minutes.from_now) # => 3 minutes ``` ### DebugHelper Returns a `pre` tag that has object dumped by YAML. This creates a very readable way to inspect an object. ```ruby my_hash = { 'first' => 1, 'second' => 'two', 'third' => [1,2,3] } debug(my_hash) ``` ```html--- first: 1 second: two third: - 1 - 2 - 3``` ### 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. You can learn more about form helpers in the [Action View Form Helpers Guide](form_helpers.html). ### JavaScriptHelper Provides functionality for working with JavaScript in your views. #### escape_javascript Escape carrier returns and single and double quotes for JavaScript segments. #### javascript_tag Returns a JavaScript tag wrapping the provided code. ```ruby javascript_tag "alert('All is good')" ``` ```html ``` ### NumberHelper Provides methods for converting numbers into formatted strings. Methods are provided for phone numbers, currency, percentage, precision, positional notation, and file size. #### number_to_currency Formats a number into a currency string (e.g., $13.65). ```ruby number_to_currency(1234567890.50) # => $1,234,567,890.50 ``` #### 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. ```ruby number_to_human(1234) # => 1.23 Thousand number_to_human(1234567) # => 1.23 Million ``` #### number_to_human_size Formats the bytes in size into a more understandable representation; useful for reporting file sizes to users. ```ruby number_to_human_size(1234) # => 1.21 KB number_to_human_size(1234567) # => 1.18 MB ``` #### number_to_percentage Formats a number as a percentage string. ```ruby number_to_percentage(100, precision: 0) # => 100% ``` #### number_to_phone Formats a number into a phone number (US by default). ```ruby number_to_phone(1235551234) # => 123-555-1234 ``` #### number_with_delimiter Formats a number with grouped thousands using a delimiter. ```ruby number_with_delimiter(12345678) # => 12,345,678 ``` #### number_with_precision Formats a number with the specified level of `precision`, which defaults to 3. ```ruby number_with_precision(111.2345) # => 111.235 number_with_precision(111.2345, precision: 2) # => 111.23 ``` ### SanitizeHelper The SanitizeHelper module provides a set of methods for scrubbing text of undesired HTML elements. #### sanitize This sanitize helper will HTML encode all tags and strip all attributes that aren't specifically allowed. ```ruby sanitize @article.body ``` If either the `:attributes` or `:tags` options are passed, only the mentioned attributes and tags are allowed and nothing else. ```ruby 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: ```ruby class Application < Rails::Application config.action_view.sanitized_allowed_tags = 'table', 'tr', 'td' end ``` #### sanitize_css(style) Sanitizes a block of CSS code. #### strip_links(html) Strips all link tags from text leaving just the link text. ```ruby strip_links('Ruby on Rails') # => Ruby on Rails ``` ```ruby strip_links('emails to me@email.com.') # => emails to me@email.com. ``` ```ruby strip_links('Blog: Visit.') # => Blog: Visit. ``` #### strip_tags(html) Strips all HTML tags from the html, including comments. This functionality is powered by the rails-html-sanitizer gem. ```ruby strip_tags("Strip these tags!") # => Strip these tags! ``` ```ruby strip_tags("Bold no more! See more") # => Bold no more! See more ``` NB: The output may still contain unescaped '<', '>', '&' characters and confuse browsers. ### UrlHelper Provides methods to make links and get URLs that depend on the routing subsystem. #### url_for Returns the URL for the set of `options` provided. ##### Examples ```ruby url_for @profile # => /profiles/1 url_for [ @hotel, @booking, page: 2, line: 3 ] # => /hotels/1/bookings/1?line=3&page=2 ``` #### link_to 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** ```ruby link_to "Profile", @profile # => Profile ``` You can use a block as well if your link target can't fit in the name parameter. ERB example: ```html+erb <%= link_to @profile do %> <%= @profile.name %> -- Check it out! <% end %> ``` would output: ```html David -- Check it out! ``` See [the API Documentation for more information](https://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to) #### button_to Generates a form that submits to the passed URL. The form has a submit button with the value of the `name`. ##### Examples ```html+erb <%= button_to "Sign in", sign_in_path %> ``` would roughly output something like: ```html ``` See [the API Documentation for more information](https://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-button_to) ### CsrfHelper Returns meta tags "csrf-param" and "csrf-token" with the name of the cross-site request forgery protection parameter and token, respectively. ```html <%= csrf_meta_tags %> ``` NOTE: Regular forms generate hidden fields so they do not use these tags. More details can be found in the [Rails Security Guide](security.html#cross-site-request-forgery-csrf).