class ActionView::Template

Action View Template¶ ↑

Constants

LEADING_ENCODING_REGEXP
NONE
STRICT_LOCALS_REGEX

Attributes

format[R]

frozen_string_literal[RW]

handler[R]

identifier[R]

variable[R]

variant[R]

virtual_path[R]

Public Class Methods

mime_types_implementation=(implementation) click to toggle source

# File lib/action_view/template.rb, line 183
def mime_types_implementation=(implementation)
  # This method isn't thread-safe, but it's not supposed
  # to be called after initialization
  if self::Types != implementation
    remove_const(:Types)
    const_set(:Types, implementation)
  end
end

new(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil) click to toggle source

# File lib/action_view/template.rb, line 198
def initialize(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil)
  @source            = source.dup
  @identifier        = identifier
  @handler           = handler
  @compiled          = false
  @locals            = locals
  @virtual_path      = virtual_path

  @variable = if @virtual_path
    base = @virtual_path.end_with?("/") ? "" : ::File.basename(@virtual_path)
    base =~ /\A_?(.*?)(?:\.\w+)*\z/
    $1.to_sym
  end

  @format            = format
  @variant           = variant
  @compile_mutex     = Mutex.new
  @strict_locals     = NONE
  @strict_local_keys = nil
  @type              = nil
end

Public Instance Methods

encode!() click to toggle source

This method is responsible for properly setting the encoding of the source. Until this point, we assume that the source is BINARY data. If no additional information is supplied, we assume the encoding is the same as Encoding.default_external.

The user can also specify the encoding via a comment on the first line of the template (# encoding: NAME-OF-ENCODING). This will work with any template engine, as we process out the encoding comment before passing the source on to the template engine, leaving a blank line in its stead.

# File lib/action_view/template.rb, line 320
def encode!
  source = self.source

  return source unless source.encoding == Encoding::BINARY

  # Look for # encoding: *. If we find one, we'll encode the
  # String in that encoding, otherwise, we'll use the
  # default external encoding.
  if source.sub!(LEADING_ENCODING_REGEXP, "")
    encoding = magic_encoding = $1
  else
    encoding = Encoding.default_external
  end

  # Tag the source with the default external encoding
  # or the encoding specified in the file
  source.force_encoding(encoding)

  # If the user didn't specify an encoding, and the handler
  # handles encodings, we simply pass the String as is to
  # the handler (with the default_external tag)
  if !magic_encoding && @handler.respond_to?(:handles_encoding?) && @handler.handles_encoding?
    source
  # Otherwise, if the String is valid in the encoding,
  # encode immediately to default_internal. This means
  # that if a handler doesn't handle encodings, it will
  # always get Strings in the default_internal
  elsif source.valid_encoding?
    source.encode!
  # Otherwise, since the String is invalid in the encoding
  # specified, raise an exception
  else
    raise WrongEncodingError.new(source, encoding)
  end
end

inspect() click to toggle source

# File lib/action_view/template.rb, line 299
def inspect
  "#<#{self.class.name} #{short_identifier} locals=#{locals.inspect}>"
end

local_assigns() click to toggle source

Returns a hash with the defined local variables.

Given this sub template rendering:

<%= render "application/header", { headline: "Welcome", person: person } %>

You can use local_assigns in the sub templates to access the local variables:

local_assigns[:headline] # => "Welcome"

Each key in local_assigns is available as a partial-local variable:

local_assigns[:headline] # => "Welcome"
headline                 # => "Welcome"

Since local_assigns is a Hash, it's compatible with Ruby 3.1's pattern matching assignment operator:

local_assigns => { headline:, **options }
headline                 # => "Welcome"
options                  # => {}

Pattern matching assignment also supports variable renaming:

local_assigns => { headline: title }
title                    # => "Welcome"

If a template refers to a variable that isn't passed into the view as part of the locals: { ... } Hash, the template will raise an ActionView::Template::Error:

<%# => raises ActionView::Template::Error %>
<% alerts.each do |alert| %>
  <p><%= alert %></p>
<% end %>

Since local_assigns returns a Hash instance, you can conditionally read a variable, then fall back to a default value when the key isn't part of the locals: { ... } options:

<% local_assigns.fetch(:alerts, []).each do |alert| %>
  <p><%= alert %></p>
<% end %>

Combining Ruby 3.1's pattern matching assignment with calls to +Hash#with_defaults+ enables compact partial-local variable assignments:

<% local_assigns.with_defaults(alerts: []) => { headline:, alerts: } %>

<h1><%= headline %></h1>

<% alerts.each do |alert| %>
  <p><%= alert %></p>
<% end %>

By default, templates will accept any locals as keyword arguments and make them available to local_assigns. To restrict what local_assigns a template will accept, add a locals: magic comment:

<%# locals: (headline:, alerts: []) %>

<h1><%= headline %></h1>

<% alerts.each do |alert| %>
  <p><%= alert %></p>
<% end %>

Read more about strict locals in Action View Overview in the guides.

# File lib/action_view/template.rb, line 164
eager_autoload do
  autoload :Error
  autoload :RawFile
  autoload :Renderable
  autoload :Handlers
  autoload :HTML
  autoload :Inline
  autoload :Types
  autoload :Sources
  autoload :Text
  autoload :Types
end

locals() click to toggle source

The locals this template has been or will be compiled for, or nil if this is a strict locals template.

# File lib/action_view/template.rb, line 222
def locals
  if strict_locals?
    nil
  else
    @locals
  end
end

render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block) click to toggle source

Render a template. If the template was not compiled yet, it is done exactly before rendering.

This method is instrumented as “!render_template.action_view”. Notice that we use a bang in this instrumentation because you don't want to consume this in production. This is only slow if it's being listened to.

# File lib/action_view/template.rb, line 270
def render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block)
  instrument_render_template do
    compile!(view)

    if strict_locals? && @strict_local_keys && !implicit_locals.empty?
      locals_to_ignore = implicit_locals - @strict_local_keys
      locals.except!(*locals_to_ignore)
    end

    if buffer
      view._run(method_name, self, locals, buffer, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)
      nil
    else
      result = view._run(method_name, self, locals, OutputBuffer.new, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)
      result.is_a?(OutputBuffer) ? result.to_s : result
    end
  end
rescue => e
  handle_render_error(view, e)
end

short_identifier() click to toggle source

# File lib/action_view/template.rb, line 295
def short_identifier
  @short_identifier ||= defined?(Rails.root) ? identifier.delete_prefix("#{Rails.root}/") : identifier
end

source() click to toggle source

# File lib/action_view/template.rb, line 303
def source
  @source.to_s
end

strict_locals!() click to toggle source

This method is responsible for marking a template as having strict locals which means the template can only accept the locals defined in a magic comment. For example, if your template accepts the locals title and comment_count, add the following to your template file:

<%# locals: (title: "Default title", comment_count: 0) %>

Strict locals are useful for validating template arguments and for specifying defaults.

# File lib/action_view/template.rb, line 365
def strict_locals!
  if @strict_locals == NONE
    self.source.sub!(STRICT_LOCALS_REGEX, "")
    @strict_locals = $1

    return if @strict_locals.nil? # Magic comment not found

    @strict_locals = "**nil" if @strict_locals.blank?
  end

  @strict_locals
end

strict_locals?() click to toggle source

Returns whether a template is using strict locals.

# File lib/action_view/template.rb, line 379
def strict_locals?
  strict_locals!
end

supports_streaming?() click to toggle source

Returns whether the underlying handler supports streaming. If so, a streaming buffer may be passed when it starts rendering.

# File lib/action_view/template.rb, line 260
def supports_streaming?
  handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
end

translate_location(backtrace_location, spot) click to toggle source

Translate an error location returned by ErrorHighlight to the correct source location inside the template.

# File lib/action_view/template.rb, line 250
def translate_location(backtrace_location, spot)
  if handler.respond_to?(:translate_location)
    handler.translate_location(spot, backtrace_location, encode!) || spot
  else
    spot
  end
end

type() click to toggle source

# File lib/action_view/template.rb, line 291
def type
  @type ||= Types[format]
end

Private Instance Methods

compile!(view) click to toggle source

Compile a template. This method ensures a template is compiled just once and removes the source after it is compiled.

# File lib/action_view/template.rb, line 417
def compile!(view)
  return if @compiled

  # Templates can be used concurrently in threaded environments
  # so compilation and any instance variable modification must
  # be synchronized
  @compile_mutex.synchronize do
    # Any thread holding this lock will be compiling the template needed
    # by the threads waiting. So re-check the @compiled flag to avoid
    # re-compilation
    return if @compiled

    mod = view.compiled_method_container

    instrument("!compile_template") do
      compile(mod)
    end

    @compiled = true
  end
end

compiled_source() click to toggle source

This method compiles the source of the template. The compilation of templates involves setting strict_locals! if applicable, encoding the template, and setting frozen string literal.

# File lib/action_view/template.rb, line 442
def compiled_source
  set_strict_locals = strict_locals!
  source = encode!
  code = @handler.call(self, source)

  method_arguments =
    if set_strict_locals
      if set_strict_locals.include?("&")
        "local_assigns, output_buffer, #{set_strict_locals}"
      else
        "local_assigns, output_buffer, #{set_strict_locals}, &_"
      end
    else
      "local_assigns, output_buffer, &_"
    end

  # Make sure that the resulting String to be eval'd is in the
  # encoding of the code
  source = +<<-end_src

find_node_by_id(node, node_id) click to toggle source

# File lib/action_view/template.rb, line 404
def find_node_by_id(node, node_id)
  return node if node.node_id == node_id

  node.children.grep(node.class).each do |child|
    found = find_node_by_id(child, node_id)
    return found if found
  end

  false
end