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 & 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.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.
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.
- cache_template_loading?
- new
- process_view_paths
- template
- template_format
- view_paths=
- with_template
- xss_safe?
- Helpers
- Partials
- ::ERB::Util
- CompiledTemplates
[RW] | assigns | |
[RW] | base_path | |
[RW] | controller | |
[R] | helpers | |
[RW] | output_buffer | |
[RW] | template_extension | |
[W] | template_format | |
[R] | view_paths |
[ show source ]
# File actionpack/lib/action_view/base.rb, line 195 195: def self.cache_template_loading? 196: ActionController::Base.allow_concurrency || (cache_template_loading.nil? ? !ActiveSupport::Dependencies.load? : cache_template_loading) 197: end
[ show source ]
# File actionpack/lib/action_view/test_case.rb, line 6 6: def initialize(*args) 7: @_rendered = { :template => nil, :partials => Hash.new(0) } 8: initialize_without_template_tracking(*args) 9: end
[ show source ]
# File actionpack/lib/action_view/base.rb, line 209 209: def self.process_view_paths(value) 210: ActionView::PathSet.new(Array(value)) 211: end
:nodoc:
[ show source ]
# File actionpack/lib/action_view/base.rb, line 191 191: def self.xss_safe? 192: false 193: end
Access the current template being rendered. Returns a ActionView::Template object.
[ show source ]
# File actionpack/lib/action_view/base.rb, line 295 295: def template 296: @_current_render 297: end
The format to be used when choosing between multiple templates with the same name but differing formats. See +Request#template_format+ for more details.
[ show source ]
# File actionpack/lib/action_view/base.rb, line 283 283: def template_format 284: if defined? @template_format 285: @template_format 286: elsif controller && controller.respond_to?(:request) 287: @template_format = controller.request.template_format.to_sym 288: else 289: @template_format = :html 290: end 291: end
[ show source ]
# File actionpack/lib/action_view/base.rb, line 239 239: def view_paths=(paths) 240: @view_paths = self.class.process_view_paths(paths) 241: # we might be using ReloadableTemplates, so we need to let them know this a new request 242: @view_paths.load! 243: end
[ show source ]
# File actionpack/lib/action_view/base.rb, line 304 304: def with_template(current_template) 305: last_template, self.template = template, current_template 306: yield 307: ensure 308: self.template = last_template 309: end