Action View Template

Namespace

Module

Methods

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)

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 171
      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
πŸ”Ž See on GitHub

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

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 186
    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
      @type              = nil
    end
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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.

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 290
    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
πŸ”Ž See on GitHub

inspect()

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 269
    def inspect
      "#<#{self.class.name} #{short_identifier} locals=#{locals.inspect}>"
    end
πŸ”Ž 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, 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 %>
πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 152
    eager_autoload do
      autoload :Error
      autoload :RawFile
      autoload :Renderable
      autoload :Handlers
      autoload :HTML
      autoload :Inline
      autoload :Types
      autoload :Sources
      autoload :Text
      autoload :Types
    end
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locals()

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

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 209
    def locals
      if strict_locals?
        nil
      else
        @locals
      end
    end
πŸ”Ž See on GitHub

render(view, locals, buffer = nil, 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€œ!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.

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 247
    def render(view, locals, buffer = nil, add_to_stack: true, &block)
      instrument_render_template do
        compile!(view)
        if buffer
          view._run(method_name, self, locals, buffer, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)
          nil
        else
          view._run(method_name, self, locals, OutputBuffer.new, add_to_stack: add_to_stack, has_strict_locals: strict_locals?, &block)&.to_s
        end
      end
    rescue => e
      handle_render_error(view, e)
    end
πŸ”Ž See on GitHub

short_identifier()

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 265
    def short_identifier
      @short_identifier ||= defined?(Rails.root) ? identifier.delete_prefix("#{Rails.root}/") : identifier
    end
πŸ”Ž See on GitHub

source()

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 273
    def source
      @source.to_s
    end
πŸ”Ž 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.

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 335
    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
πŸ”Ž See on GitHub

strict_locals?()

Returns whether a template is using strict locals.

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 349
    def strict_locals?
      strict_locals!
    end
πŸ”Ž See on GitHub

supports_streaming?()

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

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 237
    def supports_streaming?
      handler.respond_to?(:supports_streaming?) && handler.supports_streaming?
    end
πŸ”Ž See on GitHub

translate_location(backtrace_location, spot)

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

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 227
    def translate_location(backtrace_location, spot)
      if handler.respond_to?(:translate_location)
        handler.translate_location(spot, backtrace_location, encode!) || spot
      else
        spot
      end
    end
πŸ”Ž See on GitHub

type()

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 261
    def type
      @type ||= Types[format]
    end
πŸ”Ž See on GitHub

Instance Private methods

instrument(action, &block)

πŸ“ Source code 
# File actionview/lib/action_view/template.rb, line 530
      def instrument(action, &block) # :doc:
        ActiveSupport::Notifications.instrument("#{action}.action_view", instrument_payload, &block)
      end
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