Shortcode

Shortcode is a ruby gem for parsing Wordpress style shortcodes, I created it while building a CMS for a client through my ruby consultancy, Kernow Soul. The gem uses a PEG (Parsing Expression Grammar) parser rather than using regular expressions so its easier to understand, test and extend.

Installation

Add this line to your application's Gemfile:

gem 'shortcode'

And then execute:

$ bundle

Or install it yourself as:

$ gem install shortcode

Shortcode is tested against ruby version 2.5, and 2.6 as well as jruby (2.x compatible), it is not tested against ruby 2.4 or lower. Shortcode rails integration is tested against Rails versions 5.1 and 5.2.

Usage

Example

Shortcode is very simple to use, simply call the process method and pass it a string containing shortcode markup.

You can create multiple instances of Shortcode with separate configurations for each.

shortcode = Shortcode.new
shortcode.process("[quote]Hello World[/quote]")

In a Rails app, you can create helper methods to handle your shortcoded content and use them in your views with something similar to <%= content_html @page.content %>. Those two helper method can be used if your content contains html to be escaped or not.

module PagesHelper
  def content(c)
    Shortcode.process(c)
  end

  def content_html(c)
    raw content(c)
  end
end

Tags

Any tags you wish to use with Shortcode need to be configured in the setup block, there are 2 types of tag, block_tags and self_closing_tags. Block tags have a matching open and close tag such as [quote]A quote[/quote], self closing tags have no close tag, for example [gallery]. To define the tags Shortcode should parse do so in the configuration (in a Rails initializer for example) as follows:

shortcode = Shortcode.new
shortcode.setup do |config|
  config.block_tags = [:quote, :list]
  config.self_closing_tags = [:gallery, :widget]
end

Note that you can call the setup block multiple times if need be and add to it.

For example:

shortcode.setup do |config|
  config.block_tags << :other_tag
end

Templates

Each shortcode tag needs a template in order to translate the shortcode into html (or other output). Templates can be written in erb, haml or slim and work in a similar way to views in Rails. The main content of a tag is passed via the instance variable @content. Any attributes defined on a tag are passed in via an @attributes hash, shortcodes can have any number of attributes. For instance a quote shortcode might look like this:

[quote author="Homer Simpson"]Doh![/quote]

And the erb template to render the shortcode

<blockquote>
  <p class='quotation'>
    <%= @content %>
  </p>
  <% if @attributes[:author] %>
    <p class='citation'>
      <span class='author'>
        <%= @attributes[:author] %>
      </span>
    </p>
  <% end %>
</blockquote>

If using the gem within a Rails project you can use the Rails helper methods within templates.

Shortcodes can be nested inside other shortcodes, there are no limits imposed on the nesting depth. This can be useful when creating complex content such as a collapsible list that can have any content inside each element. We could have the following shortcodes

[collapsible_list]
  [item]
    [youtube id="12345"]
  [/item]
  [item]Hellow World[/item]
[/collapsible_list]

Three templates would be required to support the above content, [:collapsible_list, :item, :youtube]. Each template is rendered in isolation and has no knowledge of parent or child elements.

There are 2 ways templates can be used with Shortcode, the default it to load templates from the file system, an alternative approach is to pass templates to the setup block as strings.

Templates loaded from the file system

Simply create files with the extension or .erb, .haml, or .slim with a filename the same as the shortcode tag, e.g. gallery.html.erb would render a [gallery] shortcode tag. The default location for template files is app/views/shortcode_templates, if you want to load templates from a different location use the template_path config option.

Note: only 1 template parser is supported at a time, if using haml for instance all templates must be haml.

Templates set as configuration options

The alternative way to define templates is to set them using the templates config option, this option can take a hash with keys of the same name as the shortcode tags and values containing a template string. For instance:

shortcode = Shortcode.new

shortcode.setup do |config|
  config.templates = { gallery: 'template code' }
end

Note: Templates can be loaded from either the file system or the configuration templates. If check_config_templates_first is set to true (the default value) on the configuration then it will check configuration templates first, and file system templates if it doesn't find one. If check_config_templates_first is set to false on the configuration it will check for a file system template first, and then configuration templates if it doesn't find one. If it doesn't find a template in either spot then it will raise an error.

Custom Helpers

If you wish to use custom helper modules in templates you can do so by specifying the helpers in a setup block which should be an array. Methods in the helper modules will then become available within all templates.

shortcode = Shortcode.new

shortcode.setup do |config|
  config.helpers = [CustomHelper, AnotherCustomHelper]
end

Presenters

Sometimes the data passed to the template from the shortcode it not enough. Lets say you want to render a gallery of images using id numbers of images stored in a database, e.g. [gallery ids="1,2,3,4"]. This is where presenters can help, they allow you to modify the @content and @attributes variables before they are sent to the template for rendering. Presenters are simple classes that define four methods. The class method for should return the name of the shortcode (as a symbol) it should be applied to, the for method can also return an array of symbols if the presenter is to be used for multiple shortcodes. The classes initialize method received the attributes, content and additional_attributes variables. Finally the class should define content and attributes methods.

In a rails app you could return image records to the template using something like this:

class GalleryPresenter

  def self.for
    # An array can also be returned if the presenter should be applied
    # to multiple shortcodes, e.g. [:gallery, :enhanced_gallery]
    :gallery
  end

  def initialize(attributes, content, additional_attributes)
    @content = content
  end

  def content
    @content
  end

  def attributes
    { images: images }
  end

  private

  def images
    Image.where("id IN (?)", @attributes[:ids])
  end
end

Using additional attributes

At times you may want to pass through additional attributes to a presenter, for instance if you have a [gallery] shortcode tag and you want to pull out all images for a post, this can be achieved using additional attributes with a presenter.

class GalleryPresenter

  def self.for
    :gallery
  end

  def initialize(attributes, content, additional_attributes)
    @content = content
    @additional_attributes = additional_attributes
  end

  def content
    @content
  end

  def attributes
    { images: images }
  end

  private

  def images
    @additional_attributes[:images].map &:url
  end
end

The hash containing the images attribute is passed through to the presenter as the additional_attributes argument to the process method.

shortcode = Shortcode.new
shortcode.process('[gallery]', { images: @post.images })

Registering presenters

To register a presenter simply call register_presenter passing the presenter class e.g.

shortcode = Shortcode.new

# A single presenter
shortcode.register_presenter(CustomPresenter)

# Or multiple presenters in one call
shortcode.register_presenter(CustomPresenter, AnotherPresenter)

Configuration

shortcode = Shortcode.new

shortcode.setup do |config|

  # the template parser to use
  config.template_parser = :erb # :erb, :haml, :slim supported, :erb is default

  # location of the template files, default is "app/views/shortcode_templates"
  config.template_path = "support/templates/erb"

  # a hash of templates passed as strings.
  config.templates = { gallery: 'template code' }

  # a boolean option to set whether configuration templates are checked first or file system templates
  config.check_config_templates_first = true

  # an array of helper modules to make available within templates
  config.helpers = [CustomerHelper]

  # a list of block tags to support e.g. [quote]Hello World[/quote]
  config.block_tags = [:quote]

  # a list of self closing tags to support e.g. [youtube id="12345"]
  config.self_closing_tags = [:youtube]

  # the type of quotes to use for attribute values, default is double quotes (")
  config.attribute_quote_type = '"'

  # Allows quotes around attributes to be omitted
  # Defaults to true, quotes must be present around attribute values
  config.use_attribute_quotes = true
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request