# class ActionView::Base

# Action View Base¶ ↑

Action View templates can be written in several ways. If the template file has a `.erb` extension then it uses a mixture of ERb (included in Ruby) and HTML. 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`.

<%- 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 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>

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.account.url + @recent_items.url(item))
            xml.link(@person.firm.account.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.

### Attributes

view_renderer[RW]

### Public Instance Methods

cache_template_loading() click to toggle source

    # File lib/action_view/base.rb, line 153
    def cache_template_loading
      ActionView::Resolver.caching?
    end

cache_template_loading=(value) click to toggle source

    # File lib/action_view/base.rb, line 157
    def cache_template_loading=(value)
      ActionView::Resolver.caching = value
    end

process_view_paths(value) click to toggle source

    # File lib/action_view/base.rb, line 161
    def process_view_paths(value)
      value.is_a?(PathSet) ?
        value.dup : ActionView::PathSet.new(Array.wrap(value))
    end