Action View Template
Namespace
Module
Methods
- encode!
- inspect
- instrument
- local_assigns
- locals
- mime_types_implementation=
- new
- render
- short_identifier
- source
- strict_locals!
- strict_locals?
- supports_streaming?
- translate_location
- type
Constants
NONE | = | Object.new |
STRICT_LOCALS_REGEX | = | /\#\s+locals:\s+\((.*)\)/ |
Attributes
[R] | format | |
[RW] | frozen_string_literal | |
[R] | handler | |
[R] | identifier | |
[R] | variable | |
[R] | variant | |
[R] | virtual_path |
Class Public methods
mime_types_implementation=(implementation)
π Source code
# File actionview/lib/action_view/template.rb, line 185
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
π See on GitHub
new(source, identifier, handler, locals:, format: nil, variant: nil, virtual_path: nil)
π Source code
# File actionview/lib/action_view/template.rb, line 200
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
π See on GitHub
Instance Public methods
encode!()
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.
π Source code
# File actionview/lib/action_view/template.rb, line 322
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
π See on GitHub
inspect()
π Source code
# File actionview/lib/action_view/template.rb, line 301
def inspect
"#<#{self.class.name} #{short_identifier} locals=#{locals.inspect}>"
end
π See on GitHub
local_assigns
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
, itβs compatible with Ruby 3.1βs 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 isnβt 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 isnβt part of the locals: { ... }
options:
<% local_assigns.fetch(:alerts, []).each do |alert| %>
<p><%= alert %></p>
<% end %>
Combining Ruby 3.1βs 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.
π Source code
# File actionview/lib/action_view/template.rb, line 166
eager_autoload do
autoload :Error
autoload :RawFile
autoload :Renderable
autoload :Handlers
autoload :HTML
autoload :Inline
autoload :Types
autoload :Sources
autoload :Text
autoload :Types
end
π See on GitHub
locals()
The locals this template has been or will be compiled for, or nil if this is a strict locals template.
π Source code
# File actionview/lib/action_view/template.rb, line 224
def locals
if strict_locals?
nil
else
@locals
end
end
π See on GitHub
render(view, locals, buffer = nil, implicit_locals: [], add_to_stack: true, &block)
Render a template. If the template was not compiled yet, it is done exactly before rendering.
This method is instrumented as β!render_template.action_viewβ. Notice that we use a bang in this instrumentation because you donβt want to consume this in production. This is only slow if itβs being listened to.
π Source code
# File actionview/lib/action_view/template.rb, line 272
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
π See on GitHub
short_identifier()
π Source code
# File actionview/lib/action_view/template.rb, line 297
def short_identifier
@short_identifier ||= defined?(Rails.root) ? identifier.delete_prefix("#{Rails.root}/") : identifier
end
π See on GitHub
source()
π Source code
# File actionview/lib/action_view/template.rb, line 305
def source
@source.to_s
end
π See on GitHub
strict_locals!()
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 acceps 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.
π Source code
# File actionview/lib/action_view/template.rb, line 367
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
π See on GitHub
strict_locals?()
Returns whether a template is using strict locals.
π Source code
# File actionview/lib/action_view/template.rb, line 381
def strict_locals?
strict_locals!
end
π See on GitHub
supports_streaming?()
Returns whether the underlying handler supports streaming. If so, a streaming buffer may be passed when it starts rendering.
π Source code
# File actionview/lib/action_view/template.rb, line 262
def supports_streaming?
handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
end
π See on GitHub
translate_location(backtrace_location, spot)
Translate an error location returned by ErrorHighlight to the correct source location inside the template.
π Source code
# File actionview/lib/action_view/template.rb, line 252
def translate_location(backtrace_location, spot)
if handler.respond_to?(:translate_location)
handler.translate_location(spot, backtrace_location, encode!) || spot
else
spot
end
end
π See on GitHub
type()
π Source code
# File actionview/lib/action_view/template.rb, line 293
def type
@type ||= Types[format]
end
π See on GitHub
Instance Private methods
instrument(action, &block)
π Source code
# File actionview/lib/action_view/template.rb, line 579
def instrument(action, &block) # :doc:
ActiveSupport::Notifications.instrument("#{action}.action_view", instrument_payload, &block)
end
π See on GitHub