In my previous post about Liquid I never gave my project a name. Today it’s called Magnetism. It’s a pretty cool name for something that doesn’t work yet. I’ll be writing about Liquid assuming the audience is aware of what it and the Liquid syntax. Liquid consists of a few pieces. There are filters, drops, tags and blocks. This post will be going over blocks. Future posts will go over the other elements of Liquid as I add them to the Magnetism project.
What is a Liquid::Block
Liquid comes with a few blocks by default. You have if, unless and for to name a few. These wrap around template content.
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<!-- the if block -->
{% if this_case %}
do something in here.
{% endif %}
<!-- the for block -->
<ul>
{% for element in elements %}
<li>{{ element }}</li>
{% endfor %}
</ul> |
The prepackaged blocks are essential for template development, but I needed a few more so I dug through the Liquid documentation and the source code and got my hands dirty. I store my blocks in RAILS_ROOT/lib/magnetism/liquid and register them in RAILS_ROOT/config/initializers/magnetism.rb, but more on that later.
I’ve packaged my blocks in Magnetism::Liquid, but this isn’t necessary. This is how both cases would look.
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# packaged
module Magnetism
module Liquid
class HTML < ::Liquid::Block
# ...
end
end
end
# not packaged
class HTML < Liquid::Block
# ...
end |
The difference is at the line of inheritance. In my packaged class Liquid::Block is prefixed with ::, but that isn’t necessary in the second example because the class is not packaged. When creating a Liquid block two methods are called. There is the initialize method and render. At the moment I only needed render.
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# lib/magnetism/liquid/html.rb
module Magnetism
module Liquid
class HTML < ::Liquid::Block
def render(context)
return <<-EOF
<!DOCTYPE HTML>
<html>
#{super}
</html>
EOF
end
end
end
end |
The render method always has Liquid::Context passed into it. Even though I’m not using context in my render method I still needed to define it so render wouldn’t error. Within render the super method returns any code contained in your custom block.
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<!-- index.liquid -->
{% html %}
<body>
<h1>My Liquid Template</h1>
</body>
{% endhtml %} |
This isn’t all Liquid blocks can do, but that’s all I’ve needed for Magnetism thus far. I’ll revisit Liquid blocks and explain Liquid::Context when I work on the comments form. Stay tuned for more!
