An advance in templating technology

April 12, 2012

There are a few challenges in developing a templating engine, and I think I’ve solved one of them for this framework: including templates inside other templates.

To include another template, you use something like the following syntax:

<%= template_name( yaml: or, ruby: hash, to: be, passed: to, the: template ) %>

You might be able to tell just by looking at it, but I’ll explain anyway: that there is an ERB block (similar things are found in PHP and ASP, both Classic and .NET), which prints the result of the Ruby expression between the <% and %> brackets. The = is what tells the interpreter to print instead of just executing the code. The template name is called as a function, which is received along with the hash as an argument to the call to method_missing which will happen because the class doing the interpreting has no method with that name. As a result, templates or hash keys that are the same as Ruby reserved words or method namess of the Object class won’t work.

This is a little bit more ‘code-y’ than I would have liked, but if you look through the history of this post you’ll see that on my previous attempt I tried to roll my own templating language. That emphatically failed to work well - it simply wouldn’t extend to do the things I wanted to do. So after much head banging and head scratching I decided to use ERB instead.

You can see it all in action here (remember to click on the “Source” link at the bottom) - a template call is used to insert the photo.