Why DRYML?

Posted by Tom on 2006-11-10

DRYML: The Dont-Repeat-Yourself Markup Language. In case you hadn’t guessed, we’re intending to bring a higher level of re-use to Rails’ views.

Why? Rails already has a bunch of mechanisms for re-use within views. Namely: layouts, partials and helpers. Each serves a different purpose, and yet, IMHO, there’s still a gap. I find that small fragments of mark-up tend to crop up over and over in my views. Yes I could extract them into paritals or helpers, but I find myself disinclined to do so.

Helpers are good for small bits of dynamic content, but not so convenient for re-use of HTML fragments - I don’t really want to embed loads of HTML in strings in Ruby source. Nor do I want to make excessive use of the tag helper. I want to put mark-up in mark-up files.

So partials would be appropriate. But each partial needs it’s own file, which again discourages me from making heavy use of them.

Finally, and prefixed with a big ol’ IMHO – dang are those ERB scriptlets ever ugly! If you ever needed to call a helper passing in HTML mark-up in the parameters, that’s HTML within Ruby within HTML – not pretty. Hey, it works right? This is not a criticism of ERB. The syntax used (<%= ... %>) is like that for a reason. ERB doesn’t need fixing. DRYML supports ERB scriptlets, but allows you to hide them away behind nice clean custom tags, leaving you with beautiful clean templates [swoon] where you can see what’s going on at a glance.

Defining a tag essentially just creates a new helper method for you, and a use of that tag is nothing more than a call to that helper. This is just syntax. Witness:

hello_world.dryml

<def tag="hello">Hello World!</def>

<p>Here it is: <hello/></p>
  
<p>And here it is again: <%= hello %></p>

Groovy baby :-)

(check out the Hello World post to see how to get set up so you can try this)

And just as you can call a tag from Ruby instead of mark-up, you can define them in Ruby if you wish. You can do so in your helpers. Try this

app/helpers/application_helper.rb

module ApplicationHelper

  include Hobo::DefineTags

  def_tag :from_ruby do
    "As easy as that eh?"
  end

end

That will give you a <from_ruby/> tag in all of your DRYML templates. If your tag contains more code than mark-up, it’s cleaner to define it in a module like this.

You could even define the tag in a helper module and call it from an ERB scriptlet, but that would be kinda strange… Hey – knock yourself out, it’s all good :-)

I’m trying not to get ahead of myself because there’s a Quick Guide to DRYML coming right up. I just want to show you that this is just a thin layer on top of your regular Rails template. They’re just purdier is all.

Actually there’s a lot more under the hood in DRYML – it’s not just syntax. We’ll get there.



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