ActionDispatch::Http::MimeNegotiation

Namespace

Class

ActionDispatch::Http::MimeNegotiation::InvalidType

Methods

accepts
content_mime_type
format
format=
formats
formats=
negotiate_mime
should_apply_vary_header?
variant
variant=

Constants

BROWSER_LIKE_ACCEPTS	=	/,\s\\/\\|\\/\\s,/
	We use normal content negotiation unless you include / in your list, in which case we assume you’re a browser and send HTML.
RESCUABLE_MIME_FORMAT_ERRORS	=	[ ActionController::BadRequest, ActionDispatch::Http::Parameters::ParseError, ]

Instance Public methods

`accepts()`

Returns the accepted MIME type for the request.

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 42
def accepts
  fetch_header("action_dispatch.request.accepts") do |k|
    header = get_header("HTTP_ACCEPT").to_s.strip

    v = if header.empty?
      [content_mime_type]
    else
      Mime::Type.parse(header)
    end
    set_header k, v
  rescue ::Mime::Type::InvalidMimeType => e
    raise InvalidType, e.message
  end
end

🔎 See on GitHub

`content_mime_type()`

The MIME type of the HTTP request, such as Mime.

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 24
def content_mime_type
  fetch_header("action_dispatch.request.content_type") do |k|
    v = if get_header("CONTENT_TYPE") =~ /^([^,;]*)/
      Mime::Type.lookup($1.strip.downcase)
    else
      nil
    end
    set_header k, v
  rescue ::Mime::Type::InvalidMimeType => e
    raise InvalidType, e.message
  end
end

🔎 See on GitHub

`format(_view_path = nil)`

Returns the MIME type for the format used in the request.

# GET /posts/5.xml
request.format # => Mime[:xml]

# GET /posts/5.xhtml
request.format # => Mime[:html]

# GET /posts/5
request.format # => Mime[:html] or Mime[:js], or request.accepts.first

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 68
def format(_view_path = nil)
  formats.first || Mime::NullType.instance
end

🔎 See on GitHub

`format=(extension)`

Sets the format by string extension, which can be used to force custom formats that are not controlled by the extension.

class ApplicationController < ActionController::Base
  before_action :adjust_format_for_iphone

  private
    def adjust_format_for_iphone
      request.format = :iphone if request.env["HTTP_USER_AGENT"][/iPhone/]
    end
end

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 174
def format=(extension)
  parameters[:format] = extension.to_s
  set_header "action_dispatch.request.formats", [Mime::Type.lookup_by_extension(parameters[:format])]
end

🔎 See on GitHub

`formats()`

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 72
def formats
  fetch_header("action_dispatch.request.formats") do |k|
    v = if params_readable?
      Array(Mime[parameters[:format]])
    elsif use_accept_header && valid_accept_header
      accepts.dup
    elsif extension_format = format_from_path_extension
      [extension_format]
    elsif xhr?
      [Mime[:js]]
    else
      [Mime[:html]]
    end

    v.select! do |format|
      format.symbol || format.ref == "*/*"
    end

    set_header k, v
  end
end

🔎 See on GitHub

`formats=(extensions)`

Sets the formats by string extensions. This differs from format= by allowing you to set multiple, ordered formats, which is useful when you want to have a fallback.

In this example, the :iphone format will be used if it’s available, otherwise it’ll fall back to the :html format.

class ApplicationController < ActionController::Base
  before_action :adjust_format_for_iphone_with_html_fallback

  private
    def adjust_format_for_iphone_with_html_fallback
      request.formats = [ :iphone, :html ] if request.env["HTTP_USER_AGENT"][/iPhone/]
    end
end

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 194
def formats=(extensions)
  parameters[:format] = extensions.first.to_s
  set_header "action_dispatch.request.formats", extensions.collect { |extension|
    Mime::Type.lookup_by_extension(extension)
  }
end

🔎 See on GitHub

`negotiate_mime(order)`

Returns the first MIME type that matches the provided array of MIME types.

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 202
def negotiate_mime(order)
  formats.each do |priority|
    if priority == Mime::ALL
      return order.first
    elsif order.include?(priority)
      return priority
    end
  end

  order.include?(Mime::ALL) ? format : nil
end

🔎 See on GitHub

`should_apply_vary_header?()`

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 214
def should_apply_vary_header?
  !params_readable? && use_accept_header && valid_accept_header
end

🔎 See on GitHub

`variant()`

Returns the variant for the response template as an instance of ActiveSupport::ArrayInquirer.

request.variant = :phone
request.variant.phone?  # => true
request.variant.tablet? # => false

request.variant = [:phone, :tablet]
request.variant.phone?                  # => true
request.variant.desktop?                # => false
request.variant.any?(:phone, :desktop)  # => true
request.variant.any?(:desktop, :watch)  # => false

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 159
def variant
  @variant ||= ActiveSupport::ArrayInquirer.new
end

🔎 See on GitHub

`variant=(variant)`

Sets the variant for the response template.

When determining which template to render, Action View will incorporate all variants from the request. For example, if an ArticlesController#index action needs to respond to request.variant = [:ios, :turbo_native], it will render the first template file it can find in the following list:

app/views/articles/index.html+ios.erb
app/views/articles/index.html+turbo_native.erb
app/views/articles/index.html.erb

Variants add context to the requests that views render appropriately. Variant names are arbitrary, and can communicate anything from the request’s platform (:android, :ios, :linux, :macos, :windows) to its browser (:chrome, :edge, :firefox, :safari), to the type of user (:admin, :guest, :user).

Note: Adding many new variant templates with similarities to existing template files can make maintaining your view code more difficult.

`Parameters`

variant - a symbol name or an array of symbol names for variants used to render the response template

Examples

class ApplicationController < ActionController::Base
  before_action :determine_variants

  private
    def determine_variants
      variants = []

      # some code to determine the variant(s) to use

      variants << :ios if request.user_agent.include?("iOS")
      variants << :turbo_native if request.user_agent.include?("Turbo Native")

      request.variant = variants
    end
end

📝 Source code

# File actionpack/lib/action_dispatch/http/mime_negotiation.rb, line 137
def variant=(variant)
  variant = Array(variant)

  if variant.all?(Symbol)
    @variant = ActiveSupport::ArrayInquirer.new(variant)
  else
    raise ArgumentError, "request.variant must be set to a Symbol or an Array of Symbols."
  end
end

🔎 See on GitHub

Definition files

actionpack/lib/action_dispatch/http/mime_negotiation.rb