Class: ActionView::Base

Inherits:
Object show all
Includes:
CompiledTemplates, ERB::Util
Defined in:
lib/action_view/base.rb,
lib/action_view/helpers/form_helper.rb,
lib/action_view/helpers/active_record_helper.rb

Overview

Action View templates can be written in three ways. If the template file has a .erb (or .rhtml) extension then it uses a mixture of ERb (included in Ruby) and HTML. If the template file has a .builder (or .rxml) 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>
<% for person in @people %>
  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:

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

If you absolutely must write from within a function, you can use the TextHelper#concat.

<%- and -%> suppress leading and trailing whitespace, including the trailing newline, and can be used interchangeably with <% and %>.

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 %>

If you need to find out whether a certain local variable has been assigned a value in a particular render call, you need to use the following pattern:

<% if local_assigns.has_key? :headline %>
  Headline: <%= headline %>
<% end %>

Testing using defined? headline will not work. This is an implementation restriction.

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.

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 {
  xml.h1(@person.name)
  xml.p(@person.bio)
}

would produce something like:

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

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"

    for item in @recent_items
      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

More builder documentation can be found at builder.rubyforge.org.

JavaScriptGenerator

JavaScript templates end in .js.erb. Work like conventional erb templates which are used to render the results of an action, but these templates can generate instructions on how to modify an already rendered page. This makes it easy to modify multiple elements on your page in one declarative Ajax response. Actions with these templates are called in the background with Ajax and make updates to the page where the request originated from.

When an .js.erb action is called with link_to_remote, the generated JavaScript is automatically evaluated. Example:

link_to_function("Delete", "new Ajax.Request('delete', { method: 'DELETE' })");

The subsequently rendered delete.js.erb might look like:

$('sidebar').inner_html = '<%=j render :partial => "sidebar" %>';
Element.remove('person-<%= @person.id %>');
new Effect.Highlight('user-list');

This refreshes the sidebar, removes a person element and highlights the user list.

Defined Under Namespace

Modules: CompiledTemplates Classes: ObjectWrapper

Constant Summary collapse

@@erb_trim_mode =

Specify trim mode for the ERB compiler. Defaults to ‘-’. See ERb documentation for suitable values.

'-'
@@cache_template_loading =

Specify whether file modification times should be checked to see if a template needs recompilation

false
@@erb_variable = 
'_erbout'
@@method_names = 
{}
@@template_args =

Map method names to the names passed in local assigns so far

{}
@@computed_public_paths = 
{}
@@field_error_proc = 
Proc.new{ |html_tag, instance| "<div class=\"fieldWithErrors\">#{html_tag}</div>" }

Constants included from ERB::Util

ERB::Util::HTML_ESCAPE, ERB::Util::JSON_ESCAPE

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from ERB::Util

#html_escape, j, json_escape

Constructor Details

#initialize(view_paths = [], assigns_for_first_render = {}, controller = nil) ⇒ Base

:nodoc:



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# File 'lib/action_view/base.rb', line 216

def initialize(view_paths = [], assigns_for_first_render = {}, controller = nil)#:nodoc:
  @assigns = assigns_for_first_render
  @assigns_added = nil
  @controller = controller
  @finder = TemplateFinder.new(self, view_paths)
end

Instance Attribute Details

#assigns ⇒ Object

Returns the value of attribute assigns.



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# File 'lib/action_view/base.rb', line 154

def assigns
  @assigns
end

#base_path ⇒ Object

Returns the value of attribute base_path.



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# File 'lib/action_view/base.rb', line 154

def base_path
  @base_path
end

#controller ⇒ Object

Returns the value of attribute controller.



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# File 'lib/action_view/base.rb', line 155

def controller
  @controller
end

#current_render_extension ⇒ Object

Returns the value of attribute current_render_extension.



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# File 'lib/action_view/base.rb', line 158

def current_render_extension
  @current_render_extension
end

#finder ⇒ Object (readonly)

Returns the value of attribute finder.



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# File 'lib/action_view/base.rb', line 153

def finder
  @finder
end

#first_render ⇒ Object

Returns the value of attribute first_render.



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# File 'lib/action_view/base.rb', line 154

def first_render
  @first_render
end

#template_extension ⇒ Object

Returns the value of attribute template_extension.



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# File 'lib/action_view/base.rb', line 154

def template_extension
  @template_extension
end

#template_format ⇒ Object

Returns a symbolized version of the :format parameter of the request, or :html by default.

EXCEPTION: If the :format parameter is not set, the Accept header will be examined for whether it contains the JavaScript mime type as its first priority. If that’s the case, it will be used. This ensures that Ajax applications can use the same URL to support both JavaScript and non-JavaScript users.



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# File 'lib/action_view/base.rb', line 291

def template_format
  return @template_format if @template_format

  if controller && controller.respond_to?(:request)
    parameter_format = controller.request.parameters[:format]
    case
    when parameter_format.blank? && !controller.request.xml_http_request?
      @template_format = :html
    when parameter_format.blank? && controller.request.xml_http_request?
      @template_format = :js
    else
      @template_format = parameter_format.to_sym
    end
  else
    @template_format = :html
  end
end

Class Method Details

.cache_template_extensions=(*args) ⇒ Object 



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# File 'lib/action_view/base.rb', line 169

def self.cache_template_extensions=(*args)
  ActiveSupport::Deprecation.warn("config.action_view.cache_template_extensions option has been deprecated and has no affect. " <<
                                   "Please remove it from your config files.", caller)
end

.helper_modules ⇒ Object

:nodoc:



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

def self.helper_modules #:nodoc:
  helpers = []
  Dir.entries(File.expand_path("#{File.dirname(__FILE__)}/helpers")).sort.each do |file|
    next unless file =~ /^([a-z][a-z_]*_helper).rb$/
    require "action_view/helpers/#{$1}"
    helper_module_name = $1.camelize
    if Helpers.const_defined?(helper_module_name)
      helpers << Helpers.const_get(helper_module_name)
    end
  end
  return helpers
end

Instance Method Details

#file_public?(template_path) ⇒ Boolean

Returns true is the file may be rendered implicitly.

Returns:

  • (Boolean) 


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# File 'lib/action_view/base.rb', line 280

def file_public?(template_path)#:nodoc:
  template_path.split('/').last[0,1] != '_'
end

#render(options = {}, local_assigns = {}, &block) ⇒ Object

Renders the template present at template_path (relative to the view_paths array). The hash in local_assigns is made available as local variables.



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# File 'lib/action_view/base.rb', line 245

def render(options = {}, local_assigns = {}, &block) #:nodoc:
  if options.is_a?(String)
    render_file(options, true, local_assigns)
  elsif options.is_a?(Hash)
    use_full_path = options[:use_full_path]
    options = options.reverse_merge(:locals => {}, :use_full_path => true)

    if partial_layout = options.delete(:layout)
      if block_given?
        wrap_content_for_layout capture(&block) do 
          concat(render(options.merge(:partial => partial_layout)), block.binding)
        end
      else
        wrap_content_for_layout render(options) do
          render(options.merge(:partial => partial_layout))
        end
      end
    elsif options[:file]
      render_file(options[:file], use_full_path || false, options[:locals])
    elsif options[:partial] && options[:collection]
      render_partial_collection(options[:partial], options[:collection], options[:spacer_template], options[:locals])
    elsif options[:partial]
      render_partial(options[:partial], ActionView::Base::ObjectWrapper.new(options[:object]), options[:locals])
    elsif options[:inline]
      template = InlineTemplate.new(self, options[:inline], options[:locals], options[:type])
      render_template(template)
    end
  end
end

#render_file(template_path, use_full_path = true, local_assigns = {}) ⇒ Object

Renders the template present at template_path. If use_full_path is set to true, it’s relative to the view_paths array, otherwise it’s absolute. The hash in local_assigns is made available as local variables.



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# File 'lib/action_view/base.rb', line 226

def render_file(template_path, use_full_path = true, local_assigns = {}) #:nodoc:
  if defined?(ActionMailer) && defined?(ActionMailer::Base) && controller.is_a?(ActionMailer::Base) && !template_path.include?("/")
    raise ActionViewError, <<-END_ERROR
Due to changes in ActionMailer, you need to provide the mailer_name along with the template name.

  render "user_mailer/signup"
  render :file => "user_mailer/signup"

If you are rendering a subtemplate, you must now use controller-like partial syntax:

  render :partial => 'signup' # no mailer_name necessary
    END_ERROR
  end
  
  Template.new(self, template_path, use_full_path, local_assigns).render_template
end

#render_template(template) ⇒ Object

:nodoc:



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# File 'lib/action_view/base.rb', line 275

def render_template(template) #:nodoc:
  template.render_template
end