‘Iacta alea est’
In a previous post I attempted to introduce helper methods into the Hypertext DSL and came up short. I had been trying to introduce the methods into the Hypertext::DSL context and failing.
Having had the opportunity to sleep on it and some more time to think about it, it struck me that that Hypertext DSL is tiny. So instead of mixing a context into the Hypertext DSL, what if we mix the Hypertext DSL into the context.
Rather than use the Hypertext::DSL class, we can simply lift the code into a module, dsl.rb:
require "hypertext"
module DSL
TAGS = [:a, :abbr, :address, :area, :article, :aside,
:audio, :b, :base, :bdi, :bdo, :blockquote, :body, :br,
:button, :canvas, :caption, :cite, :code, :col, :colgroup,
:data, :datalist, :dd, :del, :details, :dfn, :dialog, :div,
:dl, :dt, :em, :embed, :fieldset, :figcaption, :figure,
:footer, :form, :h1, :h2, :h3, :h4, :h5, :h6, :head,
:header, :hgroup, :hr, :html, :i, :iframe, :img, :input,
:ins, :kbd, :label, :legend, :li, :link, :main, :map,
:mark, :meta, :meter, :nav, :noscript, :object, :ol,
:optgroup, :option, :output, :p, :param, :picture, :pre,
:progress, :q, :rb, :rp, :rt, :rtc, :ruby, :s, :samp,
:script, :section, :select, :slot, :small, :source, :span,
:strong, :style, :sub, :summary, :sup, :table, :tbody, :td,
:template, :textarea, :tfoot, :th, :thead, :time, :title,
:tr, :track, :u, :ul, :var, :video, :wbr]
def initialize(&block)
@ht = Hypertext.new
instance_eval(&block)
end
TAGS.each do |tag_name|
define_method(tag_name) do |attributes = {}, &block|
@ht.tag(tag_name, attributes, &block)
end
end
def append(content)
@ht.append(content)
end
def text(content)
@ht.text(content)
end
def to_a
@ht.to_a
end
def to_s
@ht.to_s
end
end
The only thing I changed was class to module, the rest is precisely as it stands in the Hypertext library.
Now we can create a context class that mixes in the DSL:
require_relative "./dsl"
class Context
include DSL
def id_generator
"id-#{rand(100)}"
end
end
We’ve defined an id_generator method as a proof of concept that can be called from the template, index.ht:
html lang: "en-GB" do
head do
title do
text "Hello, World!"
end
end
body do
h1 id: id_generator do
text "Welcome"
end
end
end
This time, if we put everything together by creating an instance of the context class (including our mixed in DSL) and pass the template to it:
require_relative "./context"
def render(template)
instance_eval <<-CODE
Context.new do
#{File.read(template)}
end.to_s
CODE
end
puts render("index.ht")
Then we hit the jackpot:
<html lang="en-GB">
<head>
<title>
Hello, World!
</title>
</head>
<body>
<h1 id="id-62">
Welcome
</h1>
</body>
</html>
Notice the id-62 value for the id attribute on the h1. This has been generated at random from our context method.
So now we have a proof of concept for both variable interpolation and helper methods. I’m not sure if the paths I have trodden are the best paths that could be taken, but it’s a start at least. The DSL can be extended to include variables and to allow a higher level DSL via helper methods.
—Saturday 27th March 2021.