Question

This is how I’d like to write markup in say index.html.erb

<%= page_for "Super Cool Page" do |p| %>
    <%= p.header do %>
        Ruby is Cool
    <% end %>
    <%= p.body do %>
        Witty discourse on Ruby.
    <% end %>
    <% if page.has_sidebar? %>
        <%= p.sidebar do %>
            <ul><li>Option 1</li></ul>
        <% end %>
    <% end %>
<% end %>

Which would output

<div class="page">
    <header><h1>Super Cool Page</h1></header>
    <section>
    Witty discourse on Ruby.
    </section>
</div>

and when page.has_sidebar? is true

<div class="page">
    <header><h1>Super Cool Page</h1></header>
    <asside><ul><li>Option 1</li></ul></asside>
    <section>
    Witty discourse on Ruby.
    </section>
</div>

I’ve taken a look at the FormHelper class in rails for guidance, but it seems like I’d have to duplicate a lot of work which I’m trying to avoid. I’m really just trying to figure out where to hang the classes/modules/methods in the framework and whit kind of object |p| should be.

My first inclination was to create a PageBuilder class that implements header, body and sidebar methods. But I got stuck on the rendering pipeline to get everything output just right.

Is there a gem that already provides this type of semantic generation? If not I’d love any insight on how to set this up.

Answer 1

I use something similar in my templates. Here’s a modification. This should work in Rails 3.

application_helper.rb:

module ApplicationHelper
  class PageBuilder
    def initialize(title, template)
      @title, @template = title, template
      @header, @body, @sidebar = nil, nil, nil
      @options = { :page => {} , :header => {}, :sidebar => {}, :body => {}, :title => {} } 
      @logger = Rails.logger
    end
    def parse(&block)
      if block_given?
        if @template.respond_to?(:is_haml?) && @template.is_haml?
          contents = @template.capture_haml(&block) 
        else
          #erb
          contents = @template.capture(&block)
        end
      else
        contents = ""
      end
      contents
    end

    def page (options,&block)
      options[:class] ||= "page"
      @options[:page] = options
      parse(&block)
      content = ""
      content += @template.content_tag(:title, @options[:title]) { @title } unless @title.nil?
      content += @template.content_tag(:header,@options[:header]) do
        @template.content_tag( :h1) { @header } 
      end unless @header.nil?
      content += @template.content_tag(:asside, @options[:sidebar]) { @sidebar } unless @sidebar.nil?
      content += @template.content_tag(:section, @options[:section]) { @body } unless @body.nil?
      return @template.content_tag(:div, @options[:page]) { content.html_safe }
    end
    def header(options={},&block)
      @options[:header] = options
      @header = parse(&block)
      nil
    end
    def sidebar(options={},&block)
      @options[:sidebar] = options
      @sidebar = parse(&block)
      nil
    end
    def body(options={},&block)
      @options[:body] = options
      @body = parse(&block)
      nil
    end
  end

  def page_for(title, options = {}, &block )
    raise ArgumentError, "Missing block" unless block_given?
    builder = PageBuilder.new(title, view_context )
    return builder.page(options) do 
      block.call(builder)
    end
  end
end

Now, in your sample code, when page.has_sidebar? == false, you will get

<div class="page"><title>Super Cool Page</title><header><h1>
    Ruby is Cool
</h1></header><section>
    Witty discourse on Ruby.
</section></div>

and when page.has_sidebar? == true, you will get

<div class="page"><title>Super Cool Page</title><header><h1>
    Ruby is Cool
</h1></header><asside>
      <ul><li>Option 1</li></ul>
</asside><section>
    Witty discourse on Ruby.
</section></div>

You can rearrange stuff in the page method to get any desired layout as the output.