Fluid

Fluid is a document generating system that uses Shopify's Liquid templating language.

NOTE: This shard is currently a Work in Progress for 2 reasons. First, it heavily depends on liquid.cr which is also marked as WIP. Second, I'm still developing how the interface for the classes and mixins will work, so breaking changes should be expected. During this time, I welcome any feedback on what would be most useful to the community.

Fluid uses mixins to parse and render Liquid templates for classes. Common types, such as HTMLable and Textable are already provided, and others can easily be created to extend the capabilities of Fluid.

Installation

Add the dependency to your shard.yml:

dependencies:
  fluid:
    github: HCLarsen/fluid

Run shards install

Usage

The Liquid template for a Document can either be provided as a string, or from an external file. If neither one is provided for all the required templates, a compile time error will occur.

require "fluid"

class Greeting < Fluid::Document
  include Fluid::Textable

  @@text_template_source = "Hello {{name}}"

  def initialize(@name : String)
  end
end

OR:

class Greeting < Fluid::Document
  include Fluid::Textable

  @@text_template_source = File.open("src/templates/greeting.liquid.txt")
end

Multiple mixins can be used in the same class, to provide multiple output options for a single class.

class Greeting
  include Fluid::Textable
  include Fluid::HTMLable

  @@text_template_source = "Hello {{name}}"
  @@html_template_source = %(<p class="salutation">Hello {{name}}</p>)

  def initialize(@name : String)
  end
end

greeting = Greeting.new("Chris")
greeting.to_text  #=> "Hello Chris"
greeting.to_html  #=> "<p class=\"salutation\">Hello World!</p>"

All instance variables for the class are available to the template by the same name, without the @ sign. This is how the @name ivar was able to be passed in where the template listed name in the example above. In addition, the Context for the template is an instance variable, allowing anything to be added to it through the lifecycle of the object. Please see the liquid.cr repository for the allowable types for Liquid::Any.

Rendering Other Templates

Currently, Fluid doesn't allow for use of Liquid's render command. However, any Document can be included in any other Document as a partial, provided that the included Document has the right output format. This is done by initializing the included Document, and using the Fluid::Context annotation. This adds a variable to the context with a name of render_xxx where xxx is the name of the Document's class. For instance, the example below will provide a render_greeting value to be used in the Letter template.

class Letter < Fluid::Document
  include Fluid::Textable

  @@text_template_source = File.open("#{__DIR__}/templates/letter.liquid.txt")

  @[LiquidPlay::Context]
  @greeting : Greeting
end