Module: ActionView::Helpers::AssetTagHelper
- Defined in:
- lib/action_view/helpers/asset_tag_helper.rb
Overview
This module provides methods for generating HTML that links views to assets such as images, javascripts, stylesheets, and feeds. These methods do not verify the assets exist before linking to them.
Using asset hosts
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 ActionController::Base.asset_host in your config/environment.rb
. For example, let’s say your asset host is assets.example.com
.
ActionController::Base.asset_host = "assets.example.com"
image_tag("rails.png")
=> <img src="http://assets.example.com/images/rails.png" alt="Rails" />
stylesheet_link_tag("application")
=> <link href="http://assets.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />
This is useful since browsers typically open at most two connections to a single host, which means your assets often wait in single file for their turn to load. You can alleviate this by using a %d
wildcard in asset_host
(for example, “assets%d.example.com”) to automatically distribute asset requests among four hosts (e.g., “assets0.example.com” through “assets3.example.com”) so browsers will open eight connections rather than two.
image_tag("rails.png")
=> <img src="http://assets0.example.com/images/rails.png" alt="Rails" />
stylesheet_link_tag("application")
=> <link href="http://assets3.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />
To do this, you can either setup 4 actual hosts, or you can use wildcard DNS to CNAME the wildcard to a single asset host. You can read more about setting up your DNS CNAME records from your ISP.
Note: This is purely a browser performance optimization and is not meant for server load balancing. See www.die.net/musings/page_load_time/ for background.
Alternatively, you can exert more control over the asset host by setting asset_host
to a proc that takes a single source argument. This is useful if you are unable to setup 4 actual hosts or have fewer/more than 4 hosts. The example proc below generates assets1.example.com and assets2.example.com randomly.
ActionController::Base.asset_host = Proc.new { |source| "http://assets#{rand(2) + 1}.example.com" }
image_tag("rails.png")
=> <img src="http://assets2.example.com/images/rails.png" alt="Rails" />
stylesheet_link_tag("application")
=> <link href="http://assets1.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />
The proc takes a source
parameter (which is the path of the source asset) and an optional request
parameter (which is an entire instance of an ActionController::AbstractRequest
subclass). This can be used to generate a particular asset host depending on the asset path and the particular request.
ActionController::Base.asset_host = Proc.new { |source|
if source.starts_with?('/images')
"http://images.example.com"
else
"http://assets.example.com"
end
}
image_tag("rails.png")
=> <img src="http://images.example.com/images/rails.png" alt="Rails" />
stylesheet_link_tag("application")
=> <link href="http://assets.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />
The optional request
parameter to the proc is useful in particular for serving assets from an SSL-protected page. The example proc below disables asset hosting for HTTPS connections, while still sending assets for plain HTTP requests from asset hosts. This is useful for avoiding mixed media warnings when serving non-HTTP assets from HTTPS web pages when you don’t have an SSL certificate for each of the asset hosts.
ActionController::Base.asset_host = Proc.new { |source, request|
if request.ssl?
"#{request.protocol}#{request.host_with_port}"
else
"#{request.protocol}assets.example.com"
end
}
Using asset timestamps
By default, Rails will append all asset paths with that asset’s timestamp. This allows you to set a cache-expiration date for the asset far into the future, but still be able to instantly invalidate it by simply updating the file (and hence updating the timestamp, which then updates the URL as the timestamp is part of that, which in turn busts the cache).
It’s the responsibility of the web server you use to set the far-future expiration date on cache assets that you need to take advantage of this feature. Here’s an example for Apache:
# Asset Expiration ExpiresActive On <FilesMatch “.(ico|gif|jpe?g|png|js|css)$”>
ExpiresDefault "access plus 1 year"
</FilesMatch>
Also note that in order for this to work, all your application servers must return the same timestamps. This means that they must have their clocks synchronized. If one of them drift out of sync, you’ll see different timestamps at random and the cache won’t work. Which means that the browser will request the same assets over and over again even thought they didn’t change. You can use something like Live HTTP Headers for Firefox to verify that the cache is indeed working (and that the assets are not being requested over and over).
Constant Summary collapse
- ASSETS_DIR =
defined?(Rails.public_path) ? Rails.public_path : "public"
- JAVASCRIPTS_DIR =
"#{ASSETS_DIR}/javascripts"
- STYLESHEETS_DIR =
"#{ASSETS_DIR}/stylesheets"
- JAVASCRIPT_DEFAULT_SOURCES =
[]
- @@javascript_expansions =
{ :defaults => JAVASCRIPT_DEFAULT_SOURCES.dup }
- @@stylesheet_expansions =
{}
Class Method Summary collapse
-
.register_javascript_expansion(expansions) ⇒ Object
Register one or more javascript files to be included when
symbol
is passed tojavascript_include_tag
. -
.register_javascript_include_default(*sources) ⇒ Object
Register one or more additional JavaScript files to be included when
javascript_include_tag :defaults
is called. -
.register_stylesheet_expansion(expansions) ⇒ Object
Register one or more stylesheet files to be included when
symbol
is passed tostylesheet_link_tag
. -
.reset_javascript_include_default ⇒ Object
:nodoc:.
Instance Method Summary collapse
-
#auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {}) ⇒ Object
Returns a link tag that browsers and news readers can use to auto-detect an RSS or ATOM feed.
-
#image_path(source) ⇒ Object
(also: #path_to_image)
Computes the path to an image asset in the public images directory.
-
#image_tag(source, options = {}) ⇒ Object
Returns an html image tag for the
source
. -
#javascript_include_tag(*sources) ⇒ Object
Returns an html script tag for each of the
sources
provided. -
#javascript_path(source) ⇒ Object
(also: #path_to_javascript)
Computes the path to a javascript asset in the public javascripts directory.
-
#stylesheet_link_tag(*sources) ⇒ Object
Returns a stylesheet link tag for the sources specified as arguments.
-
#stylesheet_path(source) ⇒ Object
(also: #path_to_stylesheet)
Computes the path to a stylesheet asset in the public stylesheets directory.
Class Method Details
.register_javascript_expansion(expansions) ⇒ Object
Register one or more javascript files to be included when symbol
is passed to javascript_include_tag
. This method is typically intended to be called from plugin initialization to register javascript files that the plugin installed in public/javascripts
.
ActionView::Helpers::AssetTagHelper.register_javascript_expansion :monkey => ["head", "body", "tail"]
javascript_include_tag :monkey # =>
<script type="text/javascript" src="/javascripts/head.js"></script>
<script type="text/javascript" src="/javascripts/body.js"></script>
<script type="text/javascript" src="/javascripts/tail.js"></script>
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 249 def self.register_javascript_expansion(expansions) @@javascript_expansions.merge!(expansions) end |
.register_javascript_include_default(*sources) ⇒ Object
Register one or more additional JavaScript files to be included when javascript_include_tag :defaults
is called. This method is typically intended to be called from plugin initialization to register additional .js files that the plugin installed in public/javascripts
.
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 272 def self.register_javascript_include_default(*sources) @@javascript_expansions[:defaults].concat(sources) end |
.register_stylesheet_expansion(expansions) ⇒ Object
Register one or more stylesheet files to be included when symbol
is passed to stylesheet_link_tag
. This method is typically intended to be called from plugin initialization to register stylesheet files that the plugin installed in public/stylesheets
.
ActionView::Helpers::AssetTagHelper.register_stylesheet_expansion :monkey => ["head", "body", "tail"]
stylesheet_link_tag :monkey # =>
<link href="/stylesheets/head.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/body.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/tail.css" media="screen" rel="stylesheet" type="text/css" />
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 264 def self.register_stylesheet_expansion(expansions) @@stylesheet_expansions.merge!(expansions) end |
.reset_javascript_include_default ⇒ Object
:nodoc:
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 276 def self.reset_javascript_include_default #:nodoc: @@javascript_expansions[:defaults] = JAVASCRIPT_DEFAULT_SOURCES.dup end |
Instance Method Details
#auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {}) ⇒ Object
Returns a link tag that browsers and news readers can use to auto-detect an RSS or ATOM feed. The type
can either be :rss
(default) or :atom
. Control the link options in url_for format using the url_options
. You can modify the LINK tag itself in tag_options
.
Options:
-
:rel
- Specify the relation of this link, defaults to “alternate” -
:type
- Override the auto-generated mime type -
:title
- Specify the title of the link, defaults to thetype
Examples
auto_discovery_link_tag # =>
<link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/action" />
auto_discovery_link_tag(:atom) # =>
<link rel="alternate" type="application/atom+xml" title="ATOM" href="http://www.currenthost.com/controller/action" />
auto_discovery_link_tag(:rss, {:action => "feed"}) # =>
<link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/feed" />
auto_discovery_link_tag(:rss, {:action => "feed"}, {:title => "My RSS"}) # =>
<link rel="alternate" type="application/rss+xml" title="My RSS" href="http://www.currenthost.com/controller/feed" />
auto_discovery_link_tag(:rss, {:controller => "news", :action => "feed"}) # =>
<link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/news/feed" />
auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {:title => "Example RSS"}) # =>
<link rel="alternate" type="application/rss+xml" title="Example RSS" href="http://www.example.com/feed" />
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 131 def auto_discovery_link_tag(type = :rss, = {}, = {}) tag( "link", "rel" => [:rel] || "alternate", "type" => [:type] || Mime::Type.lookup_by_extension(type.to_s).to_s, "title" => [:title] || type.to_s.upcase, "href" => .is_a?(Hash) ? url_for(.merge(:only_path => false)) : ) end |
#image_path(source) ⇒ Object Also known as: path_to_image
Computes the path to an image asset in the public images directory. Full paths from the document root will be passed through. Used internally by image_tag
to build the image path.
Examples
image_path("edit") # => /images/edit
image_path("edit.png") # => /images/edit.png
image_path("icons/edit.png") # => /images/icons/edit.png
image_path("/icons/edit.png") # => /icons/edit.png
image_path("http://www.railsapplication.com/img/edit.png") # => http://www.railsapplication.com/img/edit.png
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 375 def image_path(source) compute_public_path(source, 'images') end |
#image_tag(source, options = {}) ⇒ Object
Returns an html image tag for the source
. The source
can be a full path or a file that exists in your public images directory.
Options
You can add HTML attributes using the options
. The options
supports three additional keys for convenience and conformance:
-
:alt
- If no alt text is given, the file name part of thesource
is used (capitalized and without the extension) -
:size
- Supplied as “WidthxHeight”, so “30x45” becomes width=“30” and height=“45”.:size
will be ignored if the value is not in the correct format. -
:mouseover
- Set an alternate image to be used when the onmouseover event is fired, and sets the original image to be replaced onmouseout. This can be used to implement an easy image toggle that fires on onmouseover.
Examples
image_tag("icon") # =>
<img src="/images/icon" alt="Icon" />
image_tag("icon.png") # =>
<img src="/images/icon.png" alt="Icon" />
image_tag("icon.png", :size => "16x10", :alt => "Edit Entry") # =>
<img src="/images/icon.png" width="16" height="10" alt="Edit Entry" />
image_tag("/icons/icon.gif", :size => "16x16") # =>
<img src="/icons/icon.gif" width="16" height="16" alt="Icon" />
image_tag("/icons/icon.gif", :height => '32', :width => '32') # =>
<img alt="Icon" height="32" src="/icons/icon.gif" width="32" />
image_tag("/icons/icon.gif", :class => "menu_icon") # =>
<img alt="Icon" class="menu_icon" src="/icons/icon.gif" />
image_tag("mouse.png", :mouseover => "/images/mouse_over.png") # =>
<img src="/images/mouse.png" onmouseover="this.src='/images/mouse_over.png'" onmouseout="this.src='/images/mouse.png'" alt="Mouse" />
image_tag("mouse.png", :mouseover => image_path("mouse_over.png")) # =>
<img src="/images/mouse.png" onmouseover="this.src='/images/mouse_over.png'" onmouseout="this.src='/images/mouse.png'" alt="Mouse" />
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 413 def image_tag(source, = {}) .symbolize_keys! [:src] = path_to_image(source) [:alt] ||= File.basename([:src], '.*').split('.').first.to_s.capitalize if size = .delete(:size) [:width], [:height] = size.split("x") if size =~ %r{^\d+x\d+$} end if mouseover = .delete(:mouseover) [:onmouseover] = "this.src='#{image_path(mouseover)}'" [:onmouseout] = "this.src='#{image_path([:src])}'" end tag("img", ) end |
#javascript_include_tag(*sources) ⇒ Object
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 public/javascripts directory for inclusion into the current page or you can pass the full path relative to your document root.
Examples
javascript_include_tag "xmlhr" # =>
<script type="text/javascript" src="/javascripts/xmlhr.js"></script>
javascript_include_tag "xmlhr.js" # =>
<script type="text/javascript" src="/javascripts/xmlhr.js"></script>
javascript_include_tag "common.javascript", "/elsewhere/cools" # =>
<script type="text/javascript" src="/javascripts/common.javascript"></script>
<script type="text/javascript" src="/elsewhere/cools.js"></script>
javascript_include_tag "http://www.railsapplication.com/xmlhr" # =>
<script type="text/javascript" src="http://www.railsapplication.com/xmlhr.js"></script>
javascript_include_tag "http://www.railsapplication.com/xmlhr.js" # =>
<script type="text/javascript" src="http://www.railsapplication.com/xmlhr.js"></script>
-
The application.js file is only referenced if it exists
Though it’s not really recommended practice, if you need to extend the default JavaScript set for any reason (e.g., you’re going to be using a certain .js file in every action), then take a look at the register_javascript_include_default method.
You can also include all javascripts in the javascripts directory using :all
as the source:
javascript_include_tag :all # =>
<script type="text/javascript" src="/javascripts/application.js"></script>
<script type="text/javascript" src="/javascripts/shop.js"></script>
<script type="text/javascript" src="/javascripts/checkout.js"></script>
Note that the default javascript files will be included first. So Prototype and Scriptaculous are available to all subsequently included files.
Caching multiple javascripts into one
You can also cache multiple javascripts into one file, which requires less HTTP connections to download and can better be compressed by gzip (leading to faster transfers). Caching will only happen if ActionController::Base.perform_caching is set to true
(which is the case by default for the Rails production environment, but not for the development environment).
Examples
javascript_include_tag :all, :cache => true # when ActionController::Base.perform_caching is false =>
...
<script type="text/javascript" src="/javascripts/application.js"></script>
<script type="text/javascript" src="/javascripts/shop.js"></script>
<script type="text/javascript" src="/javascripts/checkout.js"></script>
javascript_include_tag :all, :cache => true # when ActionController::Base.perform_caching is true =>
<script type="text/javascript" src="/javascripts/all.js"></script>
javascript_include_tag "prototype", "cart", "checkout", :cache => "shop" # when ActionController::Base.perform_caching is false =>
<script type="text/javascript" src="/javascripts/prototype.js"></script>
<script type="text/javascript" src="/javascripts/cart.js"></script>
<script type="text/javascript" src="/javascripts/checkout.js"></script>
javascript_include_tag "prototype", "cart", "checkout", :cache => "shop" # when ActionController::Base.perform_caching is true =>
<script type="text/javascript" src="/javascripts/shop.js"></script>
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 223 def javascript_include_tag(*sources) = sources..stringify_keys cache = .delete("cache") if ActionController::Base.perform_caching && cache joined_javascript_name = (cache == true ? "all" : cache) + ".js" joined_javascript_path = File.join(JAVASCRIPTS_DIR, joined_javascript_name) write_asset_file_contents(joined_javascript_path, compute_javascript_paths(sources)) javascript_src_tag(joined_javascript_name, ) else (sources).collect { |source| javascript_src_tag(source, ) }.join("\n") end end |
#javascript_path(source) ⇒ Object Also known as: path_to_javascript
Computes the path to a javascript asset in the public 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.
Examples
javascript_path "xmlhr" # => /javascripts/xmlhr.js
javascript_path "dir/xmlhr.js" # => /javascripts/dir/xmlhr.js
javascript_path "/dir/xmlhr" # => /dir/xmlhr.js
javascript_path "http://www.railsapplication.com/js/xmlhr" # => http://www.railsapplication.com/js/xmlhr.js
javascript_path "http://www.railsapplication.com/js/xmlhr.js" # => http://www.railsapplication.com/js/xmlhr.js
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 152 def javascript_path(source) compute_public_path(source, 'javascripts', 'js') end |
#stylesheet_link_tag(*sources) ⇒ Object
Returns a stylesheet link tag for the sources specified as arguments. If you don’t specify an extension, .css
will be appended automatically. You can modify the link attributes by passing a hash as the last argument.
Examples
stylesheet_link_tag "style" # =>
<link href="/stylesheets/style.css" media="screen" rel="stylesheet" type="text/css" />
stylesheet_link_tag "style.css" # =>
<link href="/stylesheets/style.css" media="screen" rel="stylesheet" type="text/css" />
stylesheet_link_tag "http://www.railsapplication.com/style.css" # =>
<link href="http://www.railsapplication.com/style.css" media="screen" rel="stylesheet" type="text/css" />
stylesheet_link_tag "style", :media => "all" # =>
<link href="/stylesheets/style.css" media="all" rel="stylesheet" type="text/css" />
stylesheet_link_tag "style", :media => "print" # =>
<link href="/stylesheets/style.css" media="print" rel="stylesheet" type="text/css" />
stylesheet_link_tag "random.styles", "/css/stylish" # =>
<link href="/stylesheets/random.styles" media="screen" rel="stylesheet" type="text/css" />
<link href="/css/stylish.css" media="screen" rel="stylesheet" type="text/css" />
You can also include all styles in the stylesheet directory using :all
as the source:
stylesheet_link_tag :all # =>
<link href="/stylesheets/style1.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/styleB.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/styleX2.css" media="screen" rel="stylesheet" type="text/css" />
Caching multiple stylesheets into one
You can also cache multiple stylesheets into one file, which requires less HTTP connections and can better be compressed by gzip (leading to faster transfers). Caching will only happen if ActionController::Base.perform_caching is set to true (which is the case by default for the Rails production environment, but not for the development environment). Examples:
Examples
stylesheet_link_tag :all, :cache => true # when ActionController::Base.perform_caching is false =>
<link href="/stylesheets/style1.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/styleB.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/styleX2.css" media="screen" rel="stylesheet" type="text/css" />
stylesheet_link_tag :all, :cache => true # when ActionController::Base.perform_caching is true =>
<link href="/stylesheets/all.css" media="screen" rel="stylesheet" type="text/css" />
stylesheet_link_tag "shop", "cart", "checkout", :cache => "payment" # when ActionController::Base.perform_caching is false =>
<link href="/stylesheets/shop.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/cart.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/checkout.css" media="screen" rel="stylesheet" type="text/css" />
stylesheet_link_tag "shop", "cart", "checkout", :cache => "payment" # when ActionController::Base.perform_caching is true =>
<link href="/stylesheets/payment.css" media="screen" rel="stylesheet" type="text/css" />
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 350 def stylesheet_link_tag(*sources) = sources..stringify_keys cache = .delete("cache") if ActionController::Base.perform_caching && cache joined_stylesheet_name = (cache == true ? "all" : cache) + ".css" joined_stylesheet_path = File.join(STYLESHEETS_DIR, joined_stylesheet_name) write_asset_file_contents(joined_stylesheet_path, compute_stylesheet_paths(sources)) stylesheet_tag(joined_stylesheet_name, ) else (sources).collect { |source| stylesheet_tag(source, ) }.join("\n") end end |
#stylesheet_path(source) ⇒ Object Also known as: path_to_stylesheet
Computes the path to a stylesheet asset in the public 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.
Examples
stylesheet_path "style" # => /stylesheets/style.css
stylesheet_path "dir/style.css" # => /stylesheets/dir/style.css
stylesheet_path "/dir/style.css" # => /dir/style.css
stylesheet_path "http://www.railsapplication.com/css/style" # => http://www.railsapplication.com/css/style.css
stylesheet_path "http://www.railsapplication.com/css/style.js" # => http://www.railsapplication.com/css/style.css
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# File 'lib/action_view/helpers/asset_tag_helper.rb', line 291 def stylesheet_path(source) compute_public_path(source, 'stylesheets', 'css') end |