```
#### 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 #### date_select Returns a set of select tags (one for year, month, and day) pre-selected for accessing a specified date-based attribute. ```ruby date_select("article", "published_on") ``` #### 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. ```ruby datetime_select("article", "published_on") ``` #### 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 ``` #### select_date Returns a set of HTML select-tags (one for year, month, and day) pre-selected with the `date` provided. ```ruby # 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() ``` #### select_datetime Returns a set of HTML select-tags (one for year, month, day, hour, and minute) pre-selected with the `datetime` provided. ```ruby # 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() ``` #### select_day Returns a select tag with options for each of the days 1 through 31 with the current day selected. ```ruby # 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) ``` #### select_hour Returns a select tag with options for each of the hours 0 through 23 with the current hour selected. ```ruby # Generates a select field for hours that defaults to the hours for the time provided select_hour(Time.now + 6.hours) ``` #### select_minute Returns a select tag with options for each of the minutes 0 through 59 with the current minute selected. ```ruby # Generates a select field for minutes that defaults to the minutes for the time provided. select_minute(Time.now + 10.minutes) ``` #### select_month Returns a select tag with options for each of the months January through December with the current month selected. ```ruby # Generates a select field for months that defaults to the current month select_month(Date.today) ``` #### select_second Returns a select tag with options for each of the seconds 0 through 59 with the current second selected. ```ruby # Generates a select field for seconds that defaults to the seconds for the time provided select_second(Time.now + 16.seconds) ``` #### select_time Returns a set of HTML select-tags (one for hour and minute). ```ruby # Generates a time select that defaults to the time provided select_time(Time.now) ``` #### 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`. ```ruby # 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) ``` #### 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 ``` #### 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. ```ruby # Creates a time select tag that, when POSTed, will be stored in the order variable in the submitted attribute time_select("order", "submitted") ``` ### 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. 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: ```html+erb <%= 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: ```html ``` The params object created when this form is submitted would look like: ```ruby {"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. #### check_box Returns a checkbox tag tailored for accessing a specified attribute. ```ruby # Let's say that @article.validated? is 1: check_box("article", "validated") # => # ``` #### fields_for Creates a scope around a specific model object. This makes `fields_for` suitable for specifying additional model objects in the same form: ```html+erb <%= 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 %> ``` #### file_field Returns a file upload input tag tailored for accessing a specified attribute. ```ruby file_field(:user, :avatar) # => ``` #### 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. ```html+erb <%= form_with model: @article do |form| %> <%= form.label :title, 'Title' %>: <%= form.text_field :title %>
<%= text_field_tag 'name' %>
<% end %> # => ``` #### file_field_tag Creates a file upload field. ```html+erb <%= form_with url: new_account_avatar_path(@account), multipart: true do %> <%= file_field_tag 'avatar' %> <%= submit_tag %> <% end %> ``` Example output: ```ruby file_field_tag 'attachment' # => ``` #### 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. ```ruby hidden_field_tag 'token', 'VUBJKB23UIVI1UU1VOBVI@' # => ``` #### image_submit_tag Displays an image which when clicked will submit the form. ```ruby image_submit_tag("login.png") # => ``` #### label_tag Creates a label field. ```ruby label_tag 'name' # => ``` #### password_field_tag Creates a password field, a masked text field that will hide the users input behind a mask character. ```ruby password_field_tag 'pass' # => ``` #### 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. ```ruby radio_button_tag 'favorite_color', 'maroon' # => ``` #### select_tag Creates a dropdown selection box. ```ruby select_tag "people", "" # => ``` #### submit_tag Creates a submit button with the text provided as the caption. ```ruby submit_tag "Publish this article" # => ``` #### text_area_tag Creates a text input area; use a textarea for longer text inputs such as blog posts or descriptions. ```ruby text_area_tag 'article' # => ``` #### 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. ```ruby text_field_tag 'name' # => ``` #### email_field_tag Creates a standard input field of email type. ```ruby email_field_tag 'email' # => ``` #### url_field_tag Creates a standard input field of url type. ```ruby url_field_tag 'url' # => ``` #### date_field_tag Creates a standard input field of date type. ```ruby date_field_tag "dob" # => ``` ### 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_size Formats the bytes in size into a more understandable representation; useful for reporting file sizes to users. ```ruby number_to_human_size(1234) # => 1.2 KB number_to_human_size(1234567) # => 1.2 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).