Logic less mode

Logic less mode is inspired by Mustache. Logic less mode uses a dictionary object e.g. a recursive hash tree which contains the dynamic content.

Conditional

If the object is not false or empty?, the content will show

- article
  h1 = title

Inverted conditional

If the object is false or empty?, the content will show

-! article
  p Sorry, article not found

Iteration

If the object is an array, the section will iterate

- articles
  tr: td = title

Lambdas

Like mustache, Slim supports lambdas.

= person
  = name

The lambda method could be defined like this

def lambda_method
  "<div class='person'>#{yield(name: 'Andrew')}</div>"
end

You can optionally pass one or more hashes to yield. If you pass multiple hashes, the block will be iterated as described above.

Dictionary access

Example code:

- article
  h1 = title

The dictionary object is accessed in the order given by the :dictionary_access. Default order:

  1. :symbol - If article.respond_to?(:has_key?) and article.has_key?(:title), Slim will execute article[:title]
  2. :string - If article.respond_to?(:has_key?) and article.has_key?('title'), Slim will execute article['title']
  3. :method - If article.respond_to?(:title), Slim will execute article.send(:title)
  4. :instance_variable - If article.instance_variable_defined?(@title), Slim will execute article.instance_variable_get @title

If all the above fails, Slim will try to resolve the title reference in the same order against the parent object. In this example, the parent would be the dictionary object you are rendering the template against.

As you might have guessed, the article reference goes through the same steps against the dictionary. Instance variables are not allowed in the view code, but Slim will find and use them. Essentially, you're just dropping the @ prefix in your template. Parameterized method calls are not allowed.

Strings

The self keyword will return the .to_s value for the element under consideration.

Given

{
  article: [
    'Article 1',
    'Article 2'
  ]
}

And

- article
  tr: td = self

This will yield

<tr>
  <td>Article 1</td>
</>
<tr>
  <td>Article 2</td>
</tr>

Logic less in Rails

Install:

$ gem install slim

Require:

gem 'slim', require: 'slim/logic_less'

You might want to activate logic less mode only for a few actions, you should disable logic-less mode globally at first in the configuration

Slim::Engine.set_options logic_less: false

and activate logic less mode per render call in your action

class Controller
  def action
    Slim::Engine.with_options(logic_less: true) do
      render
    end
  end
end

Logic less in Sinatra

Sinata has built-in support for Slim. All you have to do is require the logic less Slim plugin. This can be done in your config.ru:

require 'slim/logic_less'

You are then ready to rock!

You might want to activate logic less mode only for a few actions, you should disable logic-less mode globally at first in the configuration

Slim::Engine.set_options logic_less: false

and activate logic less mode per render call in your application

get '/page'
  slim :page, logic_less: true
end

Options

Type Name Default Purpose
Boolean :logic_less true Enable logic less mode (Enabled if 'slim/logic_less' is required)
String :dictionary "self" Dictionary where variables are looked up
Symbol/Array<Symbol> :dictionary_access [:symbol, :string, :method, :instance_variable] Dictionary access order (:symbol, :string, :method, :instance_variable)