Markaby (Markup as Ruby)

Markaby is a very short bit of code for writing HTML pages in pure Ruby. It is an alternative to ERb which weaves the two languages together. Also a replacement for templating languages which use primitive languages that blend with HTML.

Using Markaby as a Rails plugin

Write Rails templates in pure Ruby. Example layout:

html do
  head do
    title 'Products: ' + action_name
    stylesheet_link_tag 'scaffold'
  end

  body do
    p flash[:notice], :style => "color: green"

    self << content_for_layout
  end
end

Markaby supports many versions of rails:

1.2.2, 1.2.3, 1.2.4, 1.2.5, 1.2.6, 2.2.0,
2.2.1, 2.2.2, 2.2.3, 2.3.1, 2.3.2, 2.3.2.1,
2.3.3, 2.3.3.1, 2.3.4

Using Markaby as a Ruby class

Markaby is flaming easy to call from your Ruby classes.

require 'markaby'

mab = Markaby::Builder.new
mab.html do
  head { title "Boats.com" }
  body do
    h1 "Boats.com has great deals"
    ul do
      li "$49 for a canoe"
      li "$39 for a raft"
      li "$29 for a huge boot that floats and can fit 5 people"
    end
  end
end
puts mab.to_s

Markaby::Builder.new does take two arguments for passing in variables and a helper object. You can also affix the block right on to the class.

See Markaby::Builder for all of that.

A Note About instance_eval

The Markaby::Builder class is different from the normal Builder class, since it uses instance_eval when running blocks. This cleans up the appearance of the Markaby code you write. If instance_eval was not used, the code would look like this:

mab = Markaby::Builder.new
mab.html do
  mab.head { mab.title "Boats.com" }
  mab.body do
    mab.h1 "Boats.com has great deals"
  end
end
puts mab.to_s

So, the advantage is the cleanliness of your code. The disadvantage is that the block will run inside the Markaby::Builder object’s scope. This means that inside these blocks, self will be your Markaby::Builder object. When you use instance variables in these blocks, they will be instance variables of the Markaby::Builder object.

This doesn’t affect Rails users, but when used in regular Ruby code, it can be a bit disorienting. You are recommended to put your Markaby code in a module where it won’t mix with anything.

The Six Steps of Markaby

If you dive right into Markaby, it’ll probably make good sense, but you’re likely to run into a few kinks. Why not review these six steps and commit them memory so you can really know what you’re doing?

1. Element Classes

Element classes may be added by hooking methods onto container elements:

div.entry do
  h2.entryTitle 'Son of WebPage'
  div.entrySection %{by Anthony}
  div.entryContent 'Okay, once again, the idea here is ...'
end

Which results in:

<div class="entry">
  <h2 class="entryTitle">Son of WebPage</h2>
  <div class="entrySection">by Anthony</div>
  <div class="entryContent">Okay, once again, the idea here is ...</div>
</div>

2. Element IDs

IDs may be added by the use of bang methods:

div.page! {
  div.content! {
    h1 "A Short Short Saintly Dog"
  }
}

Which results in:

<div id="page">
  <div id="content">
    <h1>A Short Short Saintly Dog</h1>
  </div>
</div>

3. Validate Your XHTML 1.0 Output

If you’d like Markaby to help you assemble valid XHTML documents, you can use the xhtml_transitional or xhtml_strict methods in place of the normal html tag.

xhtml_strict do
  head { ... }
  body { ... }
end

This will add the XML instruction and the doctype tag to your document. Also, a character set meta tag will be placed inside your head tag.

Now, since Markaby knows which doctype you’re using, it checks a big list of valid tags and attributes before printing anything.

>> div :styl => "padding: 10px" do
>>   img :src => "samorost.jpg"
>> end
InvalidHtmlError: no such attribute `styl'

Markaby will also make sure you don’t use the same element ID twice!

4. Escape or No Escape?

Markaby uses a simple convention for escaping stuff: if a string is an argument, it gets escaped. If the string is in a block, it doesn’t.

This is handy if you’re using something like RedCloth or RDoc inside an element. Pass the string back through the block and it’ll skip out of escaping.

div.comment { RedCloth.new(str).to_html }

But, if we have some raw text that needs escaping, pass it in as an argument:

div.comment raw_str

One caveat: if you have other tags inside a block, the string passed back will be ignored.

div.comment {
  div.author "_why"
  div.says "Torpedoooooes!"
  "<div>Silence.</div>"
}

The final div above won’t appear in the output. You can’t mix tag modes like that, friend.

5. Auto-stringification

If you end up using any of your Markaby “tags” as a string, the tag won’t be output. It’ll be up to you to add the new string back into the HTML output.

This means if you call to_s, you’ll get a string back.

div.title { "Rock Bottom" + span(" by Robert Wyatt").to_s }

But, when you’re adding strings in Ruby, to_s happens automatically.

div.title { "Rock Bottom" + span(" by Robert Wyatt") }

Interpolation works fine.

div.title { "Rock Bottom #{span(" by Robert Wyatt")}" }

And any other operation you might perform on a string.

div.menu! \
  ['5.gets', 'bits', 'cult', 'inspect', '-h'].map do |category|
    link_to category
  end.
  join( " | " )

6. The tag! Method

If you need to force a tag at any time, call tag! with the tag name followed by the possible arguments and block. The CssProxy won’t work with this technique.

tag! :select, :id => "country_list" do
  countries.each do |country|
    tag! :option, country
  end
end

A Note About Rails Helpers

When used in Rails templates, the Rails helper object is passed into Markaby::Builder. When you call helper methods inside Markaby, the output from those methods will be output to the stream. This is incredibly handy, since most Rails helpers output HTML tags.

head do
  javascript_include_tag 'prototype'
  autodiscovery_link_tag
end

However, some methods are designed to give back a String which you can use elsewhere. That’s okay! Every method returns a Fragment object, which can be used as a string.

p { "Total is: #{number_to_human_size @file_bytes}" }

Also see the Quick Tour above, specifically the stuff about auto-stringification.

If for any reason you have trouble with fragments, you can just call the @helpers object with the method and you’ll get the String back and nothing will be output.

p { "Total is: #{@helpers.number_to_human_size @file_bytes}" }

Conversely, you may call instance variables from your controller by using a method and its value will be returned, nothing will be output.

# Inside imaginary ProductController
def list
  @products = Product.find :all
end

# Inside app/views/product/list.mab
products.each do |product|
  p product.title
end

Credits

Markaby is a work of immense hope by Tim Fletcher and why the lucky stiff. It is maintained by joho, spox, and smtlaissezfaire. Thankyou for giving it a whirl.

Markaby is inspired by the HTML library within cgi.rb. Hopefully it will turn around and take some cues.