Module: ActionView::Helpers::AssetTagHelper

Includes:
AssetUrlHelper, TagHelper
Included in:
ActionView::Helpers
Defined in:
actionview/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:

image_tag("rails.png")
# => <img src="/assets/rails.png" />
stylesheet_link_tag("application")
# => <link href="/assets/application.css?body=1" rel="stylesheet" />

Constant Summary

Constants included from TagHelper

TagHelper::ARIA_PREFIXES, TagHelper::BOOLEAN_ATTRIBUTES, TagHelper::DATA_PREFIXES, TagHelper::PRE_CONTENT_STRINGS, TagHelper::TAG_TYPES

Constants included from AssetUrlHelper

ActionView::Helpers::AssetUrlHelper::ASSET_EXTENSIONS, ActionView::Helpers::AssetUrlHelper::ASSET_PUBLIC_DIRECTORIES, ActionView::Helpers::AssetUrlHelper::URI_REGEXP

Instance Method Summary collapse

Methods included from TagHelper

build_tag_values, #cdata_section, #content_tag, #escape_once, #tag, #token_list

Methods included from OutputSafetyHelper

#raw, #safe_join, #to_sentence

Methods included from CaptureHelper

#capture, #content_for, #content_for?, #provide, #with_output_buffer

Methods included from AssetUrlHelper

#asset_path, #asset_url, #audio_path, #audio_url, #compute_asset_extname, #compute_asset_host, #compute_asset_path, #font_path, #font_url, #image_path, #image_url, #javascript_path, #javascript_url, #stylesheet_path, #stylesheet_url, #video_path, #video_url

Instance Method Details

#audio_tag(*sources) ⇒ Object

Returns an HTML audio tag for the sources. If sources is a string, a single audio tag will be returned. If sources is an array, an audio tag with nested source tags for each source will be returned. The sources can be full paths, files that exist in your public audios directory, or Active Storage attachments.

When the last parameter is a hash you can add HTML attributes using that parameter.

audio_tag("sound")
# => <audio src="/audios/sound"></audio>
audio_tag("sound.wav")
# => <audio src="/audios/sound.wav"></audio>
audio_tag("sound.wav", autoplay: true, controls: true)
# => <audio autoplay="autoplay" controls="controls" src="/audios/sound.wav"></audio>
audio_tag("sound.wav", "sound.mid")
# => <audio><source src="/audios/sound.wav" /><source src="/audios/sound.mid" /></audio>

Active Storage blobs (audios that are uploaded by the users of your app):

audio_tag(user.name_pronunciation_audio)
# => <img src="/rails/active_storage/blobs/.../name_pronunciation_audio.mp4" />

496
497
498
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 496

def audio_tag(*sources)
  multiple_sources_tag_builder("audio", sources)
end

Returns a link tag that browsers and feed readers can use to auto-detect an RSS, Atom, or JSON feed. The type can be :rss (default), :atom, or :json. 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 the type

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(:json)
# => <link rel="alternate" type="application/json" title="JSON" 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.rss" />

235
236
237
238
239
240
241
242
243
244
245
246
247
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 235

def auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {})
  if !(type == :rss || type == :atom || type == :json) && tag_options[:type].blank?
    raise ArgumentError.new("You should pass :type tag_option key explicitly, because you have passed #{type} type other than :rss, :atom, or :json.")
  end

  tag(
    "link",
    "rel"   => tag_options[:rel] || "alternate",
    "type"  => tag_options[:type] || Template::Types[type].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

Returns a link tag for a favicon managed by the asset pipeline.

If a page has no link like the one generated by this helper, browsers ask for /favicon.ico automatically, and cache the file if the request succeeds. If the favicon changes it is hard to get it updated.

To have better control applications may let the asset pipeline manage their favicon storing the file under app/assets/images, and using this helper to generate its corresponding link tag.

The helper gets the name of the favicon file as first argument, which defaults to “favicon.ico”, and also supports :rel and :type options to override their defaults, “icon” and “image/x-icon” respectively:

favicon_link_tag
# => <link href="/assets/favicon.ico" rel="icon" type="image/x-icon" />

favicon_link_tag 'myicon.ico'
# => <link href="/assets/myicon.ico" rel="icon" type="image/x-icon" />

Mobile Safari looks for a different link tag, pointing to an image that will be used if you add the page to the home screen of an iOS device. The following call would generate such a tag:

favicon_link_tag 'mb-icon.png', rel: 'apple-touch-icon', type: 'image/png'
# => <link href="/assets/mb-icon.png" rel="apple-touch-icon" type="image/png" />

276
277
278
279
280
281
282
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 276

def favicon_link_tag(source = "favicon.ico", options = {})
  tag("link", {
    rel: "icon",
    type: "image/x-icon",
    href: path_to_image(source, skip_pipeline: options.delete(:skip_pipeline))
  }.merge!(options.symbolize_keys))
end

#image_tag(source, options = {}) ⇒ Object

Returns an HTML image tag for the source. The source can be a full path, a file, or an Active Storage attachment.

Options

You can add HTML attributes using the options. The options supports additional keys for convenience and conformance:

  • :size - Supplied as “WidthxHeight” or “Number”, so “30x45” becomes width=“30” and height=“45”, and “50” becomes width=“50” and height=“50”. :size will be ignored if the value is not in the correct format.

  • :srcset - If supplied as a hash or array of [source, descriptor] pairs, each image path will be expanded before the list is formatted as a string.

Examples

Assets (images that are part of your app):

image_tag("icon")
# => <img src="/assets/icon" />
image_tag("icon.png")
# => <img src="/assets/icon.png" />
image_tag("icon.png", size: "16x10", alt: "Edit Entry")
# => <img src="/assets/icon.png" width="16" height="10" alt="Edit Entry" />
image_tag("/icons/icon.gif", size: "16")
# => <img src="/icons/icon.gif" width="16" height="16" />
image_tag("/icons/icon.gif", height: '32', width: '32')
# => <img height="32" src="/icons/icon.gif" width="32" />
image_tag("/icons/icon.gif", class: "menu_icon")
# => <img class="menu_icon" src="/icons/icon.gif" />
image_tag("/icons/icon.gif", data: { title: 'Rails Application' })
# => <img data-title="Rails Application" src="/icons/icon.gif" />
image_tag("icon.png", srcset: { "icon_2x.png" => "2x", "icon_4x.png" => "4x" })
# => <img src="/assets/icon.png" srcset="/assets/icon_2x.png 2x, /assets/icon_4x.png 4x">
image_tag("pic.jpg", srcset: [["pic_1024.jpg", "1024w"], ["pic_1980.jpg", "1980w"]], sizes: "100vw")
# => <img src="/assets/pic.jpg" srcset="/assets/pic_1024.jpg 1024w, /assets/pic_1980.jpg 1980w" sizes="100vw">

Active Storage blobs (images that are uploaded by the users of your app):

image_tag(user.avatar)
# => <img src="/rails/active_storage/blobs/.../tiger.jpg" />
image_tag(user.avatar.variant(resize_to_limit: [100, 100]))
# => <img src="/rails/active_storage/representations/.../tiger.jpg" />
image_tag(user.avatar.variant(resize_to_limit: [100, 100]), size: '100')
# => <img width="100" height="100" src="/rails/active_storage/representations/.../tiger.jpg" />

394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 394

def image_tag(source, options = {})
  options = options.symbolize_keys
  check_for_image_tag_errors(options)
  skip_pipeline = options.delete(:skip_pipeline)

  options[:src] = resolve_asset_source("image", source, skip_pipeline)

  if options[:srcset] && !options[:srcset].is_a?(String)
    options[:srcset] = options[:srcset].map do |src_path, size|
      src_path = path_to_image(src_path, skip_pipeline: skip_pipeline)
      "#{src_path} #{size}"
    end.join(", ")
  end

  options[:width], options[:height] = extract_dimensions(options.delete(:size)) if options[:size]

  options[:loading] ||= image_loading if image_loading
  options[:decoding] ||= image_decoding if image_decoding

  tag("img", options)
end

#javascript_include_tag(*sources) ⇒ Object

Returns an HTML script tag for each of the sources provided.

Sources may be paths to JavaScript files. Relative paths are assumed to be relative to assets/javascripts, full paths are assumed to be relative to the document root. Relative paths are idiomatic, use absolute paths only when needed.

When passing paths, the “.js” extension is optional. If you do not want “.js” appended to the path extname: false can be set on the options.

You can modify the HTML attributes of the script tag by passing a hash as the last argument.

When the Asset Pipeline is enabled, you can pass the name of your manifest as source, and include other JavaScript or CoffeeScript files inside the manifest.

If the server supports Early Hints header links for these assets will be automatically pushed.

Options

When the last parameter is a hash you can add HTML attributes using that parameter. The following options are supported:

  • :extname - Append an extension to the generated URL unless the extension already exists. This only applies for relative URLs.

  • :protocol - Sets the protocol of the generated URL. This option only applies when a relative URL and host options are provided.

  • :host - When a relative URL is provided the host is added to the that path.

  • :skip_pipeline - This option is used to bypass the asset pipeline when it is set to true.

  • :nonce - When set to true, adds an automatic nonce value if you have Content Security Policy enabled.

Examples

javascript_include_tag "xmlhr"
# => <script src="/assets/xmlhr.debug-1284139606.js"></script>

javascript_include_tag "xmlhr", host: "localhost", protocol: "https"
# => <script src="https://localhost/assets/xmlhr.debug-1284139606.js"></script>

javascript_include_tag "template.jst", extname: false
# => <script src="/assets/template.debug-1284139606.jst"></script>

javascript_include_tag "xmlhr.js"
# => <script src="/assets/xmlhr.debug-1284139606.js"></script>

javascript_include_tag "common.javascript", "/elsewhere/cools"
# => <script src="/assets/common.javascript.debug-1284139606.js"></script>
#    <script src="/elsewhere/cools.debug-1284139606.js"></script>

javascript_include_tag "http://www.example.com/xmlhr"
# => <script src="http://www.example.com/xmlhr"></script>

javascript_include_tag "http://www.example.com/xmlhr.js"
# => <script src="http://www.example.com/xmlhr.js"></script>

javascript_include_tag "http://www.example.com/xmlhr.js", nonce: true
# => <script src="http://www.example.com/xmlhr.js" nonce="..."></script>

89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 89

def javascript_include_tag(*sources)
  options = sources.extract_options!.stringify_keys
  path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
  preload_links = []
  nopush = options["nopush"].nil? ? true : options.delete("nopush")
  crossorigin = options.delete("crossorigin")
  crossorigin = "anonymous" if crossorigin == true
  integrity = options["integrity"]
  rel = options["type"] == "module" ? "modulepreload" : "preload"

  sources_tags = sources.uniq.map { |source|
    href = path_to_javascript(source, path_options)
    if preload_links_header && !options["defer"] && href.present? && !href.start_with?("data:")
      preload_link = "<#{href}>; rel=#{rel}; as=script"
      preload_link += "; crossorigin=#{crossorigin}" unless crossorigin.nil?
      preload_link += "; integrity=#{integrity}" unless integrity.nil?
      preload_link += "; nopush" if nopush
      preload_links << preload_link
    end
    tag_options = {
      "src" => href,
      "crossorigin" => crossorigin
    }.merge!(options)
    if tag_options["nonce"] == true
      tag_options["nonce"] = content_security_policy_nonce
    end
    ("script", "", tag_options)
  }.join("\n").html_safe

  if preload_links_header
    send_preload_links_header(preload_links)
  end

  sources_tags
end

Returns a link tag that browsers can use to preload the source. The source can be the path of a resource managed by asset pipeline, a full path, or an URI.

Options

  • :type - Override the auto-generated mime type, defaults to the mime type for source extension.

  • :as - Override the auto-generated value for as attribute, calculated using source extension and mime type.

  • :crossorigin - Specify the crossorigin attribute, required to load cross-origin resources.

  • :nopush - Specify if the use of server push is not desired for the resource. Defaults to false.

  • :integrity - Specify the integrity attribute.

Examples

preload_link_tag("custom_theme.css")
# => <link rel="preload" href="/assets/custom_theme.css" as="style" type="text/css" />

preload_link_tag("/videos/video.webm")
# => <link rel="preload" href="/videos/video.mp4" as="video" type="video/webm" />

preload_link_tag(post_path(format: :json), as: "fetch")
# => <link rel="preload" href="/posts.json" as="fetch" type="application/json" />

preload_link_tag("worker.js", as: "worker")
# => <link rel="preload" href="/assets/worker.js" as="worker" type="text/javascript" />

preload_link_tag("//example.com/font.woff2")
# => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="anonymous"/>

preload_link_tag("//example.com/font.woff2", crossorigin: "use-credentials")
# => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="use-credentials" />

preload_link_tag("/media/audio.ogg", nopush: true)
# => <link rel="preload" href="/media/audio.ogg" as="audio" type="audio/ogg" />

319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 319

def preload_link_tag(source, options = {})
  href = path_to_asset(source, skip_pipeline: options.delete(:skip_pipeline))
  extname = File.extname(source).downcase.delete(".")
  mime_type = options.delete(:type) || Template::Types[extname]&.to_s
  as_type = options.delete(:as) || resolve_link_as(extname, mime_type)
  crossorigin = options.delete(:crossorigin)
  crossorigin = "anonymous" if crossorigin == true || (crossorigin.blank? && as_type == "font")
  integrity = options[:integrity]
  nopush = options.delete(:nopush) || false
  rel = mime_type == "module" ? "modulepreload" : "preload"

  link_tag = tag.link(**{
    rel: rel,
    href: href,
    as: as_type,
    type: mime_type,
    crossorigin: crossorigin
  }.merge!(options.symbolize_keys))

  preload_link = "<#{href}>; rel=#{rel}; as=#{as_type}"
  preload_link += "; type=#{mime_type}" if mime_type
  preload_link += "; crossorigin=#{crossorigin}" if crossorigin
  preload_link += "; integrity=#{integrity}" if integrity
  preload_link += "; nopush" if nopush

  send_preload_links_header([preload_link])

  link_tag
end

Returns a stylesheet link tag for the sources specified as arguments.

When passing paths, the .css extension is optional. If you don't specify an extension, .css will be appended automatically. If you do not want .css appended to the path, set extname: false in the options. You can modify the link attributes by passing a hash as the last argument.

If the server supports Early Hints header links for these assets will be automatically pushed.

Options

  • :extname - Append an extension to the generated URL unless the extension already exists. This only applies for relative URLs.

  • :protocol - Sets the protocol of the generated URL. This option only applies when a relative URL and host options are provided.

  • :host - When a relative URL is provided the host is added to the that path.

  • :skip_pipeline - This option is used to bypass the asset pipeline when it is set to true.

Examples

stylesheet_link_tag "style"
# => <link href="/assets/style.css" rel="stylesheet" />

stylesheet_link_tag "style.css"
# => <link href="/assets/style.css" rel="stylesheet" />

stylesheet_link_tag "http://www.example.com/style.css"
# => <link href="http://www.example.com/style.css" rel="stylesheet" />

stylesheet_link_tag "style.less", extname: false, skip_pipeline: true, rel: "stylesheet/less"
# => <link href="/stylesheets/style.less" rel="stylesheet/less">

stylesheet_link_tag "style", media: "all"
# => <link href="/assets/style.css" media="all" rel="stylesheet" />

stylesheet_link_tag "style", media: "print"
# => <link href="/assets/style.css" media="print" rel="stylesheet" />

stylesheet_link_tag "random.styles", "/css/stylish"
# => <link href="/assets/random.styles" rel="stylesheet" />
#    <link href="/css/stylish.css" rel="stylesheet" />

170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 170

def stylesheet_link_tag(*sources)
  options = sources.extract_options!.stringify_keys
  path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
  preload_links = []
  crossorigin = options.delete("crossorigin")
  crossorigin = "anonymous" if crossorigin == true
  nopush = options["nopush"].nil? ? true : options.delete("nopush")
  integrity = options["integrity"]

  sources_tags = sources.uniq.map { |source|
    href = path_to_stylesheet(source, path_options)
    if preload_links_header && href.present? && !href.start_with?("data:")
      preload_link = "<#{href}>; rel=preload; as=style"
      preload_link += "; crossorigin=#{crossorigin}" unless crossorigin.nil?
      preload_link += "; integrity=#{integrity}" unless integrity.nil?
      preload_link += "; nopush" if nopush
      preload_links << preload_link
    end
    tag_options = {
      "rel" => "stylesheet",
      "crossorigin" => crossorigin,
      "href" => href
    }.merge!(options)

    if apply_stylesheet_media_default && tag_options["media"].blank?
      tag_options["media"] = "screen"
    end

    tag(:link, tag_options)
  }.join("\n").html_safe

  if preload_links_header
    send_preload_links_header(preload_links)
  end

  sources_tags
end

#video_tag(*sources) ⇒ Object

Returns an HTML video tag for the sources. If sources is a string, a single video tag will be returned. If sources is an array, a video tag with nested source tags for each source will be returned. The sources can be full paths, files that exist in your public videos directory, or Active Storage attachments.

Options

When the last parameter is a hash you can add HTML attributes using that parameter. The following options are supported:

  • :poster - Set an image (like a screenshot) to be shown before the video loads. The path is calculated like the src of image_tag.

  • :size - Supplied as “WidthxHeight” or “Number”, so “30x45” becomes width=“30” and height=“45”, and “50” becomes width=“50” and height=“50”. :size will be ignored if the value is not in the correct format.

  • :poster_skip_pipeline will bypass the asset pipeline when using the :poster option instead using an asset in the public folder.

Examples

video_tag("trailer")
# => <video src="/videos/trailer"></video>
video_tag("trailer.ogg")
# => <video src="/videos/trailer.ogg"></video>
video_tag("trailer.ogg", controls: true, preload: 'none')
# => <video preload="none" controls="controls" src="/videos/trailer.ogg"></video>
video_tag("trailer.m4v", size: "16x10", poster: "screenshot.png")
# => <video src="/videos/trailer.m4v" width="16" height="10" poster="/assets/screenshot.png"></video>
video_tag("trailer.m4v", size: "16x10", poster: "screenshot.png", poster_skip_pipeline: true)
# => <video src="/videos/trailer.m4v" width="16" height="10" poster="screenshot.png"></video>
video_tag("/trailers/hd.avi", size: "16x16")
# => <video src="/trailers/hd.avi" width="16" height="16"></video>
video_tag("/trailers/hd.avi", size: "16")
# => <video height="16" src="/trailers/hd.avi" width="16"></video>
video_tag("/trailers/hd.avi", height: '32', width: '32')
# => <video height="32" src="/trailers/hd.avi" width="32"></video>
video_tag("trailer.ogg", "trailer.flv")
# => <video><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>
video_tag(["trailer.ogg", "trailer.flv"])
# => <video><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>
video_tag(["trailer.ogg", "trailer.flv"], size: "160x120")
# => <video height="120" width="160"><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>

Active Storage blobs (videos that are uploaded by the users of your app):

video_tag(user.intro_video)
# => <img src="/rails/active_storage/blobs/.../intro_video.mp4" />

464
465
466
467
468
469
470
471
472
# File 'actionview/lib/action_view/helpers/asset_tag_helper.rb', line 464

def video_tag(*sources)
  options = sources.extract_options!.symbolize_keys
  public_poster_folder = options.delete(:poster_skip_pipeline)
  sources << options
  multiple_sources_tag_builder("video", sources) do |tag_options|
    tag_options[:poster] = path_to_image(tag_options[:poster], skip_pipeline: public_poster_folder) if tag_options[:poster]
    tag_options[:width], tag_options[:height] = extract_dimensions(tag_options.delete(:size)) if tag_options[:size]
  end
end