module Roda::RodaPlugins::Render

  1. lib/roda/plugins/render.rb
  2. lib/roda/plugins/render_each.rb
  3. lib/roda/plugins/render_locals.rb
  4. lib/roda/plugins/view_options.rb
  5. show all

The render plugin adds support for template rendering using the tilt library. Two methods are provided for template rendering, view (which uses the layout) and render (which does not).

plugin :render

route do |r| 'foo' do
    view('foo') # renders views/foo.erb inside views/layout.erb
  end 'bar' do
    render('bar') # renders views/bar.erb

The render and view methods just return strings, they do not have side effects (unless the templates themselves have side effects). As Roda uses the routing block return value as the body of the response, in most cases you will call these methods as the last expression in a routing block to have the response body be the result of the template rendering.

Because render and view just return strings, you can call them inside templates (i.e. for subtemplates/partials), or multiple times in the same route and combine the results together:

route do |r| 'foo-bars' do
    @bars = Bar.where(:foo).map{|b| render(:bar, locals: {bar: b})}.join

You can provide options to the plugin method:

plugin :render, engine: 'haml', views: 'admin_views'

Plugin Options

The following plugin options are supported:


Set the template paths to allow. Attempts to render paths outside of these paths will raise an error. Defaults to the :views directory.


nil/false to explicitly disable premanent template caching. By default, permanent template caching is disabled by default if RACK_ENV is development. When permanent template caching is disabled, for templates with paths in the file system, the modification time of the file will be checked on every render, and if it has changed, a new template will be created for the current content of the file.


A class to use as the template cache instead of the default.


Can be set to false to turn off template path checking.


The tilt engine to use for rendering, also the default file extension for templates, defaults to ‘erb’.


Use Erubi as the ERB template engine, and enable escaping by default, which makes <%= %> escape output and <%== %> not escape output. If given, sets the escape: true option for all template engines, which can break some non-ERB template engines. You can use a string or array of strings as the value for this option to only set the escape: true option for those specific template engines.


The base name of the layout file, defaults to ‘layout’. This can be provided as a hash with the :template or :inline options.


The options to use when rendering the layout, if different from the default options.


The tilt options used when rendering all templates. defaults to: {outvar: '@_out_buf', default_encoding: Encoding.default_external}.


The tilt options to use per template engine. Keys are engine strings, values are hashes of template options.


The directory holding the view files, defaults to the ‘views’ subdirectory of the application’s :root option (the process’s working directory by default).

Render/View Method Options

Most of these options can be overridden at runtime by passing options to the view or render methods:

view('foo', engine: 'html.erb')
render('foo', views: 'admin_views')

There are additional options to view and render that are available at runtime:


Set to false to not cache this template, even when caching is on by default. Set to true to force caching for this template, even when the default is to not permantently cache (e.g. when using the :template_block option).


Explicitly set the hash key to use when caching.


Only respected by view, provides the content to render inside the layout, instead of rendering a template to get the content.


Use the value given as the template code, instead of looking for template code in a file.


Hash of local variables to make available inside the template.


Use the value given as the full pathname for the file, instead of using the :views and :engine option in combination with the template name.


The object in which context to evaluate the template. By default, this is the Roda instance.


Provides the name of the template to use. This allows you pass a single options hash to the render/view method, while still allowing you to specify the template name.


Pass this block when creating the underlying template, ignored when using :inline. Disables caching of the template by default.


Provides the template class to use, instead of using Tilt or Tilt[:engine].

Here’s an example of using these options:

view(inline: '<%= @foo %>')
render(path: '/path/to/template.erb')

If you pass a hash as the first argument to view or render, it should have either :template, :inline, :path, or :content (for view) as one of the keys.

Speeding Up Template Rendering

The render/view method calls are optimized for usage with a single symbol/string argument specifying the template name. So for fastest rendering, pass only a symbol/string to render/view. Next best optimized are template calls with a single :locals option. Use of other options disables the compiled template method optimizations and can be significantly slower.

If you must pass a hash to render/view, either as a second argument or as the only argument, you can speed things up by specifying a :cache_key option in the hash, making sure the :cache_key is unique to the template you are rendering.

Accepting Template Blocks in Methods

If you are used to Rails, you may be surprised that this type of template code doesn’t work in Roda:

<%= some_method do %>
  Some HTML
<% end %>

The reason this doesn’t work is that this is not valid ERB syntax, it is Rails syntax, and requires attempting to parse the some_method do Ruby code with a regular expression. Since Roda uses ERB syntax, it does not support this.

In general, these methods are used to wrap the content of the block and inject the content into the output. To get similar behavior with Roda, you have a few different options you can use.

Directly Inject Template Output

You can switch from a <%= tag to using a <% tag:

<% some_method do %>
  Some HTML
<% end %>

While this would output Some HTML into the template, it would not be able to inject content before or after the block. However, you can use the inject_erb_plugin to handle the injection:

def some_method
  inject_erb "content before block"
  inject_erb "content after block"

If you need to modify the captured block before injecting it, you can use the capture_erb plugin to capture content from the template block, and modify that content, then use inject_erb to inject it into the template output:

def some_method(&block)
  inject_erb "content before block"
  inject_erb capture_erb(&block).upcase
  inject_erb "content after block"

This is the recommended approach for handling this type of method, if you want to keep the template block in the same template.

Separate Block Output Into Separate Template

By moving the Some HTML into a separate template, you can render that template inside the block:

<%= some_method{render('template_name')} %>

It’s also possible to use an inline template:

<%= some_method do render(:inline=><<-END)
  Some HTML
end %>

This approach is useful if it makes sense to separate the template block into its own template. You lose the ability to use local variable from outside the template block inside the template block with this approach.

Separate Header and Footer

You can define two separate methods, one that outputs the content before the block, and one that outputs the content after the block, and use those instead of a single call:

<%= some_method_before %>
  Some HTML
<%= some_method_after %>

This is the simplest option to setup, but it is fairly tedious to use.


COMPILED_METHOD_SUPPORT = RUBY_VERSION >= '2.3' && tilt_compiled_method_support && ENV['RODA_RENDER_COMPILED_METHOD_SUPPORT'] != 'no'  
NO_CACHE = {:cache=>false}.freeze  

Public Class methods

configure(app, opts=OPTS)

Setup default rendering options. See Render for details.

[show source]
    # File lib/roda/plugins/render.rb
232 def self.configure(app, opts=OPTS)
233   if app.opts[:render]
234     orig_cache = app.opts[:render][:cache]
235     orig_method_cache = app.opts[:render][:template_method_cache]
236     opts = app.opts[:render][:orig_opts].merge(opts)
237   end
238   app.opts[:render] = opts.dup
239   app.opts[:render][:orig_opts] = opts
241   opts = app.opts[:render]
242   opts[:engine] = (opts[:engine] || "erb").dup.freeze
243   opts[:views] = app.expand_path(opts[:views]||"views").freeze
244   opts[:allowed_paths] ||= [opts[:views]].freeze
245   opts[:allowed_paths] = opts[:allowed_paths].map{|f| app.expand_path(f, nil)}.uniq.freeze
246   opts[:check_paths] = true unless opts.has_key?(:check_paths)
248   unless opts.has_key?(:check_template_mtime)
249     opts[:check_template_mtime] = if opts[:cache] == false || opts[:explicit_cache]
250       true
251     else
252       ENV['RACK_ENV'] == 'development'
253     end
254   end
256   begin
257     app.const_get(:RodaCompiledTemplates, false)
258   rescue NameError
259     compiled_templates_module =
260     app.send(:include, compiled_templates_module)
261     app.const_set(:RodaCompiledTemplates, compiled_templates_module)
262   end
263   opts[:template_method_cache] = orig_method_cache || (opts[:cache_class] || RodaCache).new
264   opts[:template_method_cache][:_roda_layout] = nil if opts[:template_method_cache][:_roda_layout]
265   opts[:cache] = orig_cache || (opts[:cache_class] || RodaCache).new
267   opts[:layout_opts] = (opts[:layout_opts] || {}).dup
268   opts[:layout_opts][:_is_layout] = true
269   if opts[:layout_opts][:views]
270     opts[:layout_opts][:views] = app.expand_path(opts[:layout_opts][:views]).freeze
271   end
273   if layout = opts.fetch(:layout, true)
274     opts[:layout] = true
276     case layout
277     when Hash
278       opts[:layout_opts].merge!(layout)
279     when true
280       opts[:layout_opts][:template] ||= 'layout'
281     else
282       opts[:layout_opts][:template] = layout
283     end
285     opts[:optimize_layout] = (opts[:layout_opts][:template] if opts[:layout_opts].keys.sort == [:_is_layout, :template])
286   end
287   opts[:layout_opts].freeze
289   template_opts = opts[:template_opts] = (opts[:template_opts] || {}).dup
290   template_opts[:outvar] ||= '@_out_buf'
291   unless template_opts.has_key?(:default_encoding)
292     template_opts[:default_encoding] = Encoding.default_external
293   end
295   engine_opts = opts[:engine_opts] = (opts[:engine_opts] || {}).dup
296   engine_opts.to_a.each do |k,v|
297     engine_opts[k] = v.dup.freeze
298   end
300   if escape = opts[:escape]
301     require 'tilt/erubi'
303     case escape
304     when String, Array
305       Array(escape).each do |engine|
306         engine_opts[engine] = (engine_opts[engine] || {}).merge(:escape => true).freeze
307       end
308     else
309       template_opts[:escape] = true
310     end
311   end
313   template_opts.freeze
314   engine_opts.freeze
315   opts.freeze
316 end
tilt_template_compiled_method(template, locals_keys, scope_class)
[show source]
    # File lib/roda/plugins/render.rb
220 def self.tilt_template_compiled_method(template, locals_keys, scope_class)
221   template.send(:compiled_method, locals_keys, scope_class)
222 end