Class: ActionView::Base

Inherits:
Object show all
Extended by:
ActiveSupport::Memoizable
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. If the template file has a .rjs extension then it will use ActionView::Helpers::PrototypeHelper::JavaScriptGenerator.

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

JavaScriptGenerator templates end in .rjs. Unlike conventional templates which are used to render the results of an action, these templates 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.

An instance of the JavaScriptGenerator object named page is automatically made available to your template, which is implicitly wrapped in an ActionView::Helpers::PrototypeHelper#update_page block.

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

link_to_remote :url => {:action => 'delete'}

The subsequently rendered delete.rjs might look like:

page.replace_html  'sidebar', :partial => 'sidebar'
page.remove        "person-#{@person.id}"
page.visual_effect :highlight, 'user-list'

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

See the ActionView::Helpers::PrototypeHelper::GeneratorMethods documentation for more details.

Defined Under Namespace

Modules: CompiledTemplates Classes: ProxyModule

Constant Summary collapse

@@exempt_from_layout =

Templates that are exempt from layouts

Set.new([/\.rjs$/])
@@debug_rjs =

Specify whether RJS responses should be wrapped in a try/catch block that alert()s the caught exception (and then re-raises it).

false
@@warn_cache_misses =

A warning will be displayed whenever an action results in a cache miss on your view paths.

false
@@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 222

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

Instance Attribute Details

#assignsObject

Returns the value of attribute assigns


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# File 'lib/action_view/base.rb', line 163

def assigns
  @assigns
end

#base_pathObject

Returns the value of attribute base_path


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# File 'lib/action_view/base.rb', line 163

def base_path
  @base_path
end

#controllerObject

Returns the value of attribute controller


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# File 'lib/action_view/base.rb', line 164

def controller
  @controller
end

#helpersObject (readonly)

Returns the value of attribute helpers


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

def helpers
  @helpers
end

#output_bufferObject

Returns the value of attribute output_buffer


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# File 'lib/action_view/base.rb', line 168

def output_buffer
  @output_buffer
end

#template_extensionObject

Returns the value of attribute template_extension


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# File 'lib/action_view/base.rb', line 163

def template_extension
  @template_extension
end

#template_formatObject

The format to be used when choosing between multiple templates with the same name but differing formats. See Request#template_format for more details.


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# File 'lib/action_view/base.rb', line 270

def template_format
  if defined? @template_format
    @template_format
  elsif controller && controller.respond_to?(:request)
    @template_format = controller.request.template_format
  else
    @template_format = :html
  end
end

#view_pathsObject

Returns the value of attribute view_paths


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# File 'lib/action_view/base.rb', line 231

def view_paths
  @view_paths
end

Class Method Details

.exempt_from_layout(*extensions) ⇒ Object

Don't render layouts for templates with the given extensions.


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

def self.exempt_from_layout(*extensions)
  regexps = extensions.collect do |extension|
    extension.is_a?(Regexp) ? extension : /\.#{Regexp.escape(extension.to_s)}$/
  end
  @@exempt_from_layout.merge(regexps)
end

.process_view_paths(value) ⇒ Object


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# File 'lib/action_view/base.rb', line 205

def self.process_view_paths(value)
  ActionView::PathSet.new(Array(value))
end

Instance Method Details

#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 239

def render(options = {}, local_assigns = {}, &block) #:nodoc:
  local_assigns ||= {}

  if options.is_a?(String)
    ActiveSupport::Deprecation.warn(
      "Calling render with a string will render a partial from Rails 2.3. " +
      "Change this call to render(:file => '#{options}', :locals => locals_hash)."
    )

    render(:file => options, :locals => local_assigns)
  elsif options == :update
    update_page(&block)
  elsif options.is_a?(Hash)
    options = options.reverse_merge(:locals => {})
    if options[:layout]
      _render_with_layout(options, local_assigns, &block)
    elsif options[:file]
      _pick_template(options[:file]).render_template(self, options[:locals])
    elsif options[:partial]
      render_partial(options)
    elsif options[:inline]
      InlineTemplate.new(options[:inline], options[:type]).render(self, options[:locals])
    elsif options[:text]
      options[:text]
    end
  end
end

#templateObject

Access the current template being rendered. Returns a ActionView::Template object.


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# File 'lib/action_view/base.rb', line 282

def template
  @_render_stack.last
end