Class: ActionView::Base

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

Overview

Action View templates can be written in two ways. If the template file has a .rhtml extension then it uses a mixture of ERb (included in Ruby) and HTML. If the template file has a .rxml extension then Jim Weirich’s Builder::XmlMarkup library is used.

ERb

You trigger ERb by using embeddings such as <% %> and <%= %>. The difference is whether you want output or not. 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)

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 in 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 %>

Template caching

The parsing of ERb templates are cached by default, but the reading of them are not. This means that the application by default will reflect changes to the templates immediatly. If you’d like to sacrifice that immediacy for the speed gain given by also caching the loading of templates (reading from the file system), you can turn that on with ActionView::Base.cache_template_loading = true.

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 .rxml extension.

Here are some basic examples:

xml.em("emphasized")                              # => <em>emphasized</em>
xml.em { xml.b("emp & bold") }                    # => <em><b>emph &amp; bold</b></em>
xml.a("A Link", "href"=>"http://onestepback.org") # => <a href="http://onestepback.org">A Link</a>
xm.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.

Constant Summary collapse

@@cache_template_loading =

Turn on to cache the reading of templates from the file system. Doing so means that you have to restart the server when changing templates, but that rendering will be faster.

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

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(base_path = nil, assigns_for_first_render = {}, controller = nil) ⇒ Base

:nodoc:



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# File 'lib/action_view/base.rb', line 159

def initialize(base_path = nil, assigns_for_first_render = {}, controller = nil)#:nodoc:
  @base_path, @assigns = base_path, assigns_for_first_render
  @controller = controller
end

Instance Attribute Details

#assigns ⇒ Object

Returns the value of attribute assigns.



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# File 'lib/action_view/base.rb', line 123

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 123

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 124

def controller
  @controller
end

#first_render ⇒ Object (readonly)

Returns the value of attribute first_render.



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# File 'lib/action_view/base.rb', line 122

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 123

def template_extension
  @template_extension
end

Class Method Details

.controller_delegate(*methods) ⇒ Object

:nodoc:



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# File 'lib/action_view/base.rb', line 145

def self.controller_delegate(*methods)#:nodoc:
  methods.flatten.each do |method|
    class_eval <<-end_eval
      def #{method}(*args, &block)
        controller.send(%(#{method}), *args, &block)
      end
    end_eval
  end
end

.load_helpers(helper_dir) ⇒ Object

:nodoc:



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# File 'lib/action_view/base.rb', line 135

def self.load_helpers(helper_dir)#:nodoc:
  Dir.foreach(helper_dir) do |helper_file| 
    next unless helper_file =~ /_helper.rb$/
    require helper_dir + helper_file
    helper_module_name = helper_file.capitalize.gsub(/_([a-z])/) { |m| $1.capitalize }[0..-4]

    class_eval("include ActionView::Helpers::#{helper_module_name}") if Helpers.const_defined?(helper_module_name)
  end
end

.register_template_handler(extension, klass) ⇒ Object 



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

def self.register_template_handler(extension, klass)
  @@template_handlers[extension] = klass
end

Instance Method Details

#builder_template_exists?(template_path) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/action_view/base.rb', line 233

def builder_template_exists?(template_path)#:nodoc:
  template_exists?(template_path, "rxml")
end

#delegate_template_exists?(template_path) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/action_view/base.rb', line 225

def delegate_template_exists?(template_path)#:nodoc:
  @@template_handlers.find { |k,| template_exists?(template_path, k) }
end

#erb_template_exists?(template_path) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/action_view/base.rb', line 229

def erb_template_exists?(template_path)#:nodoc:
  template_exists?(template_path, "rhtml")
end

#file_exists?(template_path) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/action_view/base.rb', line 237

def file_exists?(template_path)#:nodoc:
  erb_template_exists?(template_path) || builder_template_exists?(template_path) || delegate_template_exists?(template_path)
end

#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 242

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

#pick_rendering_method(template_extension) ⇒ Object

:nodoc:



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# File 'lib/action_view/base.rb', line 217

def pick_rendering_method(template_extension)#:nodoc:
  if @@template_handlers[template_extension]
    "delegate_render"
  else
    (template_extension == "rxml" ? "rxml" : "rhtml") + "_render"
  end
end

#pick_template_extension(template_path) ⇒ Object

:nodoc:



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

def pick_template_extension(template_path)#:nodoc:
  if match = delegate_template_exists?(template_path)
    match.first
  elsif erb_template_exists?(template_path)
    "rhtml"
  elsif builder_template_exists?(template_path)
    "rxml"
  else
    raise ActionViewError, "No rhtml, rxml, or delegate template found for #{template_path}"
  end
end

#render(template_path, local_assigns = {}) ⇒ Object

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



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# File 'lib/action_view/base.rb', line 194

def render(template_path, local_assigns = {})
  render_file(template_path, true, local_assigns)
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 template_root, 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 167

def render_file(template_path, use_full_path = true, local_assigns = {})
  @first_render      = template_path if @first_render.nil?
  
  if use_full_path
    template_extension = pick_template_extension(template_path)
    template_file_name = full_template_path(template_path, template_extension)
  else
    template_file_name = template_path
    template_extension = template_path.split(".").last
  end
  
  template_source = read_template_file(template_file_name)

  begin
    render_template(template_extension, template_source, local_assigns)
  rescue Exception => e
    if TemplateError === e
      e.sub_template_of(template_file_name)
      raise e
    else
      raise TemplateError.new(@base_path, template_file_name, @assigns, template_source, e)
    end
  end
end

#render_template(template_extension, template, local_assigns = {}) ⇒ Object

Renders the template which is given as a string as either rhtml or rxml depending on template_extension. The hash in local_assigns is made available as local variables.



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# File 'lib/action_view/base.rb', line 200

def render_template(template_extension, template, local_assigns = {})
  send(pick_rendering_method(template_extension), template_extension,
    template, local_assigns)
end