Class: ActionView::Base

Inherits:
Object show all
Includes:
Context, Helpers, ERB::Util
Defined in:
actionview/lib/action_view/base.rb

Overview

Action View Base

Action View templates can be written in several ways. If the template file has a .erb extension, then it uses the erubi template system which can embed Ruby into an HTML document. If the template file has a .builder extension, then Jim Weirich’s Builder::XmlMarkup library is used.

ERB

You trigger ERB by using embeddings such as <% %>, <% -%>, and <%= %>. The <%= %> tag set is used when you want output. Consider the following loop for names:

<b>Names of all the people</b>
<% @people.each do |person| %>
  Name: <%= person.name %><br/>
<% end %>

The loop is setup in regular embedding tags <% %>, and the name is written using the output embedding tag <%= %>. Note that this is not just a usage suggestion. Regular output functions like print or puts won’t work with ERB templates. So this would be wrong:

<%# WRONG %>
Hi, Mr. <% puts "Frodo" %>

If you absolutely must write from within a function use concat.

When on a line that only contains whitespaces except for the tag, <% %> suppresses leading and trailing whitespace, including the trailing newline. <% %> and <%- -%> are the same. Note however that <%= %> and <%= -%> are different: only the latter removes trailing whitespaces.

Using sub templates

Using sub templates allows you to sidestep tedious replication and extract common display structures in shared templates. The classic example is the use of a header and footer (even though the Action Pack-way would be to use Layouts):

<%= render "shared/header" %>
Something really specific and terrific
<%= render "shared/footer" %>

As you see, we use the output embeddings for the render methods. The render call itself will just return a string holding the result of the rendering. The output embedding writes it to the current template.

But you don’t have to restrict yourself to static includes. Templates can share variables amongst themselves by using instance variables defined using the regular embedding tags. Like this:

<% @page_title = "A Wonderful Hello" %>
<%= render "shared/header" %>

Now the header can pick up on the @page_title variable and use it for outputting a title tag:

<title><%= @page_title %></title>

Passing local variables to sub templates

You can pass local variables to sub templates by using a hash with the variable names as keys and the objects as values:

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

These can now be accessed in shared/header with:

Headline: <%= headline %>
First name: <%= person.first_name %>

The local variables passed to sub templates can be accessed as a hash using the local_assigns hash. This lets you access the variables as:

Headline: <%= local_assigns[:headline] %>

This is useful in cases where you aren’t sure if the local variable has been assigned. Alternatively, you could also use defined? headline to first check if the variable has been assigned before using it.

Template caching

By default, Rails will compile each template to a method in order to render it. When you alter a template, Rails will check the file’s modification time and recompile it in development mode.

Builder

Builder templates are a more programmatic alternative to ERB. They are especially useful for generating XML content. An XmlMarkup object named xml is automatically made available to templates with a .builder extension.

Here are some basic examples:

xml.em("emphasized")                                 # => <em>emphasized</em>
xml.em { xml.b("emph & bold") }                      # => <em><b>emph &amp; bold</b></em>
xml.a("A Link", "href" => "http://onestepback.org")  # => <a href="http://onestepback.org">A Link</a>
xml.target("name" => "compile", "option" => "fast")  # => <target option="fast" name="compile"\>
                                                     # NOTE: order of attributes is not specified.

Any method with a block will be treated as an XML markup tag with nested markup in the block. For example, the following:

xml.div do
  xml.h1(@person.name)
  xml.p(@person.bio)
end

would produce something like:

<div>
  <h1>David Heinemeier Hansson</h1>
  <p>A product of Danish Design during the Winter of '79...</p>
</div>

Here is a full-length RSS example actually used on Basecamp:

xml.rss("version" => "2.0", "xmlns:dc" => "http://purl.org/dc/elements/1.1/") do
  xml.channel do
    xml.title(@feed_title)
    xml.link(@url)
    xml.description "Basecamp: Recent items"
    xml.language "en-us"
    xml.ttl "40"

    @recent_items.each do |item|
      xml.item do
        xml.title(item_title(item))
        xml.description(item_description(item)) if item_description(item)
        xml.pubDate(item_pubDate(item))
        xml.guid(@person.firm..url + @recent_items.url(item))
        xml.link(@person.firm..url + @recent_items.url(item))

        xml.tag!("dc:creator", item.author_name) if item_has_creator?(item)
      end
    end
  end
end

For more information on Builder please consult the source code.

Direct Known Subclasses

ActionDispatch::DebugView

Constant Summary collapse

NULL = 
Object.new

Constants included from Helpers::UrlHelper

Helpers::UrlHelper::BUTTON_TAG_METHOD_VERBS

Constants included from Helpers::TagHelper

Helpers::TagHelper::BOOLEAN_ATTRIBUTES, Helpers::TagHelper::PRE_CONTENT_STRINGS, Helpers::TagHelper::TAG_PREFIXES, Helpers::TagHelper::TAG_TYPES

Constants included from Helpers::JavaScriptHelper

Helpers::JavaScriptHelper::JS_ESCAPE_MAP

Constants included from RecordIdentifier

RecordIdentifier::JOIN, RecordIdentifier::NEW

Constants included from Helpers::DateHelper

Helpers::DateHelper::MINUTES_IN_QUARTER_YEAR, Helpers::DateHelper::MINUTES_IN_THREE_QUARTERS_YEAR, Helpers::DateHelper::MINUTES_IN_YEAR

Constants included from Helpers::ControllerHelper

Helpers::ControllerHelper::CONTROLLER_DELEGATES

Constants included from Helpers::AssetUrlHelper

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

Constants included from ERB::Util

ERB::Util::HTML_ESCAPE, ERB::Util::HTML_ESCAPE_ONCE_REGEXP, ERB::Util::JSON_ESCAPE, ERB::Util::JSON_ESCAPE_REGEXP

Instance Attribute Summary collapse

Attributes included from Context

#output_buffer, #view_flow

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Helpers

eager_load!

Methods included from ActiveSupport::Concern

#append_features, #class_methods, extended, #included

Methods included from ActiveSupport::Autoload

#autoload, #autoload_at, #autoload_under, #autoloads, #eager_autoload, #eager_load!, extended

Methods included from Helpers::UrlHelper

#button_to, #current_page?, #link_to, #link_to_if, #link_to_unless, #link_to_unless_current, #mail_to, #phone_to, #sms_to, #url_for

Methods included from Helpers::TagHelper

build_tag_values, #cdata_section, #class_names, #content_tag, #escape_once, #tag

Methods included from Helpers::OutputSafetyHelper

#raw, #safe_join, #to_sentence

Methods included from Helpers::CaptureHelper

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

Methods included from Helpers::TranslationHelper

#localize, #translate

Methods included from Helpers::TextHelper

#concat, #current_cycle, #cycle, #excerpt, #highlight, #pluralize, #reset_cycle, #safe_concat, #simple_format, #truncate, #word_wrap

Methods included from Helpers::SanitizeHelper

#sanitize, #sanitize_css, #strip_links, #strip_tags

Methods included from Helpers::RenderingHelper

#_layout_for, #render

Methods included from Helpers::NumberHelper

#number_to_currency, #number_to_human, #number_to_human_size, #number_to_percentage, #number_to_phone, #number_with_delimiter, #number_with_precision

Methods included from Helpers::JavaScriptHelper

#escape_javascript, #javascript_cdata_section, #javascript_tag

Methods included from Helpers::FormTagHelper

#button_tag, #check_box_tag, #color_field_tag, #date_field_tag, #datetime_field_tag, #email_field_tag, #field_set_tag, #file_field_tag, #form_tag, #hidden_field_tag, #image_submit_tag, #label_tag, #month_field_tag, #number_field_tag, #password_field_tag, #radio_button_tag, #range_field_tag, #search_field_tag, #select_tag, #submit_tag, #telephone_field_tag, #text_area_tag, #text_field_tag, #time_field_tag, #url_field_tag, #utf8_enforcer_tag, #week_field_tag

Methods included from Helpers::FormOptionsHelper

#collection_check_boxes, #collection_radio_buttons, #collection_select, #grouped_collection_select, #grouped_options_for_select, #option_groups_from_collection_for_select, #options_for_select, #options_from_collection_for_select, #select, #time_zone_options_for_select, #time_zone_select

Methods included from Helpers::FormHelper

#check_box, #color_field, #date_field, #datetime_field, #email_field, #fields, #fields_for, #file_field, #form_for, #form_with, #hidden_field, #label, #month_field, #number_field, #password_field, #radio_button, #range_field, #search_field, #telephone_field, #text_area, #text_field, #time_field, #url_field, #week_field

Methods included from RecordIdentifier

#dom_class, #dom_id

Methods included from ModelNaming

#convert_to_model, #model_name_from_record_or_class

Methods included from Helpers::DebugHelper

#debug

Methods included from Helpers::DateHelper

#date_select, #datetime_select, #distance_of_time_in_words, #select_date, #select_datetime, #select_day, #select_hour, #select_minute, #select_month, #select_second, #select_time, #select_year, #time_ago_in_words, #time_select, #time_tag

Methods included from Helpers::CsrfHelper

#csrf_meta_tags

Methods included from Helpers::CspHelper

#csp_meta_tag

Methods included from Helpers::ControllerHelper

#assign_controller, #logger, #respond_to?

Methods included from Helpers::CacheHelper

#cache, #cache_fragment_name, #cache_if, #cache_unless, #digest_path_from_template

Methods included from Helpers::AtomFeedHelper

#atom_feed

Methods included from Helpers::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

Methods included from Helpers::AssetTagHelper

#audio_tag, #auto_discovery_link_tag, #favicon_link_tag, #image_tag, #javascript_include_tag, #preload_link_tag, #stylesheet_link_tag, #video_tag

Methods included from ActiveSupport::Benchmarkable

#benchmark

Methods included from ERB::Util

h, html_escape, html_escape_once, json_escape, unwrapped_html_escape

Methods included from Context

#_layout_for, #_prepare_context

Constructor Details

#initialize(lookup_context = nil, assigns = {}, controller = nil, formats = NULL) ⇒ Base

:startdoc:



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# File 'actionview/lib/action_view/base.rb', line 240

def initialize(lookup_context = nil, assigns = {}, controller = nil, formats = NULL) #:nodoc:
  @_config = ActiveSupport::InheritableOptions.new

  unless formats == NULL
    ActiveSupport::Deprecation.warn <<~eowarn.squish
    Passing formats to ActionView::Base.new is deprecated
    eowarn
  end

  case lookup_context
  when ActionView::LookupContext
    @lookup_context = lookup_context
  else
    ActiveSupport::Deprecation.warn <<~eowarn.squish
    ActionView::Base instances should be constructed with a lookup context,
    assignments, and a controller.
    eowarn
    @lookup_context = self.class.build_lookup_context(lookup_context)
  end

  @view_renderer = ActionView::Renderer.new @lookup_context
  @current_template = nil

  @cache_hit = {}
  assign(assigns)
  assign_controller(controller)
  _prepare_context
end

Instance Attribute Details

#lookup_context ⇒ Object (readonly)

Returns the value of attribute lookup_context



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# File 'actionview/lib/action_view/base.rb', line 198

def lookup_context
  @lookup_context
end

#view_renderer ⇒ Object (readonly)

Returns the value of attribute view_renderer



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# File 'actionview/lib/action_view/base.rb', line 198

def view_renderer
  @view_renderer
end

Class Method Details

.build_lookup_context(context) ⇒ Object

:stopdoc:



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# File 'actionview/lib/action_view/base.rb', line 209

def self.build_lookup_context(context)
  case context
  when ActionView::Renderer
    context.lookup_context
  when Array
    ActionView::LookupContext.new(context)
  when ActionView::PathSet
    ActionView::LookupContext.new(context)
  when nil
    ActionView::LookupContext.new([])
  else
    raise NotImplementedError, context.class.name
  end
end

.cache_template_loading ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 171

def cache_template_loading
  ActionView::Resolver.caching?
end

.cache_template_loading=(value) ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 175

def cache_template_loading=(value)
  ActionView::Resolver.caching = value
end

.changed?(other) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'actionview/lib/action_view/base.rb', line 193

def changed?(other) # :nodoc:
  compiled_method_container != other.compiled_method_container
end

.empty ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 224

def self.empty
  with_view_paths([])
end

.with_context(context, assigns = {}, controller = nil) ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 232

def self.with_context(context, assigns = {}, controller = nil)
  new context, assigns, controller
end

.with_empty_template_cache ⇒ Object

:nodoc:



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# File 'actionview/lib/action_view/base.rb', line 183

def with_empty_template_cache # :nodoc:
  subclass = Class.new(self) {
    # We can't implement these as self.class because subclasses will
    # share the same template cache as superclasses, so "changed?" won't work
    # correctly.
    define_method(:compiled_method_container)           { subclass }
    define_singleton_method(:compiled_method_container) { subclass }
  }
end

.with_view_paths(view_paths, assigns = {}, controller = nil) ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 228

def self.with_view_paths(view_paths, assigns = {}, controller = nil)
  with_context ActionView::LookupContext.new(view_paths), assigns, controller
end

.xss_safe? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'actionview/lib/action_view/base.rb', line 179

def xss_safe? #:nodoc:
  true
end

Instance Method Details

#_run(method, template, locals, buffer, &block) ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 269

def _run(method, template, locals, buffer, &block)
  _old_output_buffer, _old_virtual_path, _old_template = @output_buffer, @virtual_path, @current_template
  @current_template = template
  @output_buffer = buffer
  send(method, locals, buffer, &block)
ensure
  @output_buffer, @virtual_path, @current_template = _old_output_buffer, _old_virtual_path, _old_template
end

#assign(new_assigns) ⇒ Object

:nodoc:



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# File 'actionview/lib/action_view/base.rb', line 203

def assign(new_assigns) # :nodoc:
  @_assigns = new_assigns.each { |key, value| instance_variable_set("@#{key}", value) }
end

#compiled_method_container ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 278

def compiled_method_container
  if self.class == ActionView::Base
    ActiveSupport::Deprecation.warn <<~eowarn.squish
      ActionView::Base instances must implement `compiled_method_container`
      or use the class method `with_empty_template_cache` for constructing
      an ActionView::Base instance that has an empty cache.
    eowarn
  end

  self.class
end

#in_rendering_context(options) ⇒ Object 



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# File 'actionview/lib/action_view/base.rb', line 290

def in_rendering_context(options)
  old_view_renderer  = @view_renderer
  old_lookup_context = @lookup_context

  if !lookup_context.html_fallback_for_js && options[:formats]
    formats = Array(options[:formats])
    if formats == [:js]
      formats << :html
    end
    @lookup_context = lookup_context.with_prepended_formats(formats)
    @view_renderer = ActionView::Renderer.new @lookup_context
  end

  yield @view_renderer
ensure
  @view_renderer = old_view_renderer
  @lookup_context = old_lookup_context
end