WIP: Not all the helpers are listed here. For a full list see the [API documentation](https://api.rubyonrails.org/classes/ActionView/Helpers.html)
The following is only a brief overview summary of the helpers available in Action View. It's recommended that you review the [API Documentation](https://api.rubyonrails.org/classes/ActionView/Helpers.html), which covers all of the helpers in more detail, but this should serve as a good starting point.
### 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`:
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.
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.
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.
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.
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.
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.
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 %>
<p>Welcome! The date and time is <%= Time.now %></p>
<% end %>
```
The captured variable can then be used anywhere else.
```html+erb
<html>
<head>
<title>Welcome!</title>
</head>
<body>
<%= @greeting %>
</body>
</html>
```
#### 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+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**
```html+erb
<p>This is a special page.</p>
<% content_for :special_script do %>
<script>alert('Hello!')</script>
<% 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.
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.
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
<script>
//<![CDATA[
alert('All is good')
//]]>
</script>
```
### 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).
