| Module | ActionView::Helpers::AssetTagHelper |
| In: |
actionpack/lib/action_view/helpers/asset_tag_helper.rb
|
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.
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 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_include_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_include_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 four 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.
| ASSETS_DIR | = | defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/public" : "public" |
| JAVASCRIPTS_DIR | = | "#{ASSETS_DIR}/javascripts" |
| STYLESHEETS_DIR | = | "#{ASSETS_DIR}/stylesheets" |
| JAVASCRIPT_DEFAULT_SOURCES | = | ['prototype', 'effects', 'dragdrop', 'controls'] unless const_defined?(:JAVASCRIPT_DEFAULT_SOURCES) |
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.
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 206 def self.register_javascript_include_default(*sources) @@javascript_default_sources.concat(sources) end
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.
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" />
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 69 def auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {}) tag( "link", "rel" => tag_options[:rel] || "alternate", "type" => tag_options[:type] || Mime::Type.lookup_by_extension(type.to_s).to_s, "title" => tag_options[:title] || type.to_s.upcase, "href" => url_options.is_a?(Hash) ? url_for(url_options.merge(:only_path => false)) : url_options ) end
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.
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
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 326 def image_path(source) compute_public_path(source, 'images') end
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.
You can add HTML attributes using the options. The options supports two additional keys for convienence and conformance:
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" />
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 356 def image_tag(source, options = {}) options.symbolize_keys! options[:src] = image_path(source) options[:alt] ||= File.basename(options[:src], '.*').split('.').first.capitalize if options[:size] options[:width], options[:height] = options[:size].split("x") if options[:size] =~ %r{^\d+x\d+$} options.delete(:size) end tag("img", options) end
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. To include the Prototype and Scriptaculous javascript libraries in your application, pass :defaults as the source. When using :defaults, if an application.js file exists in your public javascripts directory, it will be included as well. You can modify the html attributes of the script tag by passing a hash as the last argument.
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>
javascript_include_tag :defaults # =>
<script type="text/javascript" src="/javascripts/prototype.js"></script>
<script type="text/javascript" src="/javascripts/effects.js"></script>
...
<script type="text/javascript" src="/javascripts/application.js"></script>
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/prototype.js"></script>
<script type="text/javascript" src="/javascripts/effects.js"></script>
...
<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.
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).
javascript_include_tag :all, :cache => true # when ActionController::Base.perform_caching is false =>
<script type="text/javascript" src="/javascripts/prototype.js"></script>
<script type="text/javascript" src="/javascripts/effects.js"></script>
...
<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 false =>
<script type="text/javascript" src="/javascripts/shop.js"></script>
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 174 def javascript_include_tag(*sources) options = sources.extract_options!.stringify_keys cache = options.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) if !file_exist?(joined_javascript_path) File.open(joined_javascript_path, "w+") do |cache| javascript_paths = expand_javascript_sources(sources).collect do |source| compute_public_path(source, 'javascripts', 'js', false) end cache.write(join_asset_file_contents(javascript_paths)) end end content_tag("script", "", { "type" => Mime::JS, "src" => javascript_path(joined_javascript_name) }.merge(options)) else expand_javascript_sources(sources).collect do |source| content_tag("script", "", { "type" => Mime::JS, "src" => javascript_path(source) }.merge(options)) end.join("\n") end end
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.
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
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 90 def javascript_path(source) compute_public_path(source, 'javascripts', 'js') end
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.
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" />
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:
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" />
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 283 def stylesheet_link_tag(*sources) options = sources.extract_options!.stringify_keys cache = options.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) if !file_exist?(joined_stylesheet_path) File.open(joined_stylesheet_path, "w+") do |cache| stylesheet_paths = expand_stylesheet_sources(sources).collect do |source| compute_public_path(source, 'stylesheets', 'css', false) end cache.write(join_asset_file_contents(stylesheet_paths)) end end tag("link", { "rel" => "stylesheet", "type" => Mime::CSS, "media" => "screen", "href" => html_escape(stylesheet_path(joined_stylesheet_name)) }.merge(options), false, false) else options.delete("cache") expand_stylesheet_sources(sources).collect do |source| tag("link", { "rel" => "stylesheet", "type" => Mime::CSS, "media" => "screen", "href" => html_escape(stylesheet_path(source)) }.merge(options), false, false) end.join("\n") end end
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.
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
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 225 def stylesheet_path(source) compute_public_path(source, 'stylesheets', 'css') end
Pick an asset host for this source. Returns nil if no host is set, the host if no wildcard is set, or the host interpolated with the numbers 0-3 if it contains %d. The number is the source hash mod 4.
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 421 def compute_asset_host(source) if host = ActionController::Base.asset_host host % (source.hash % 4) end end
Add the .ext if not present. Return full URLs otherwise untouched. Prefix with /dir/ if lacking a leading /. Account for relative URL roots. Rewrite the asset path for cache-busting asset ids. Include a single or wildcarded asset host, if configured, with the correct request protocol.
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 386 def compute_public_path(source, dir, ext = nil, include_host = true) cache_key = [ @controller.request.protocol, ActionController::Base.asset_host, @controller.request.relative_url_root, dir, source, ext, include_host ].join ActionView::Base.computed_public_paths[cache_key] ||= begin source += ".#{ext}" if File.extname(source).blank? && ext if source =~ %r{^[-a-z]+://} source else source = "/#{dir}/#{source}" unless source[0] == ?/ source = "#{@controller.request.relative_url_root}#{source}" rewrite_asset_path!(source) if include_host host = compute_asset_host(source) unless host.blank? or host =~ %r{^[-a-z]+://} host = "#{@controller.request.protocol}#{host}" end "#{host}#{source}" else source end end end end
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 450 def expand_javascript_sources(sources) case when sources.include?(:all) all_javascript_files = Dir[File.join(JAVASCRIPTS_DIR, '*.js')].collect { |file| File.basename(file).split(".", 0).first }.sort sources = ((@@javascript_default_sources.dup & all_javascript_files) + all_javascript_files).uniq when sources.include?(:defaults) sources = sources[0..(sources.index(:defaults))] + @@javascript_default_sources.dup + sources[(sources.index(:defaults) + 1)..sources.length] sources.delete(:defaults) sources << "application" if file_exist?(File.join(JAVASCRIPTS_DIR, "application.js")) end sources end
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 468 def expand_stylesheet_sources(sources) if sources.first == :all @@all_stylesheet_sources ||= Dir[File.join(STYLESHEETS_DIR, '*.css')].collect { |file| File.basename(file).split(".", 1).first }.sort else sources end end
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 371 def file_exist?(path) @@file_exist_cache ||= {} if !(@@file_exist_cache[path] ||= File.exist?(path)) @@file_exist_cache[path] = true false else true end end
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 476 def join_asset_file_contents(paths) paths.collect { |path| File.read(File.join(ASSETS_DIR, path.split("?").first)) }.join("\n\n") end
Use the RAILS_ASSET_ID environment variable or the source’s modification time as its cache-busting asset id.
# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 429 def rails_asset_id(source) if asset_id = ENV["RAILS_ASSET_ID"] asset_id else path = File.join(ASSETS_DIR, source) if File.exist?(path) File.mtime(path).to_i.to_s else '' end end end