Difference between single and double equals in Slim (= vs ==)

Question

In Slim, when should I use double equals sign?

For example:

== yield
== render 'partial'
== stylesheet_link_tag "application", media: "all"
title == full_title(yield(:title))

- flash.each do |key, value|
    == value

or

= yield
= render 'partial'
= stylesheet_link_tag "application", media: "all"
title == full_title(yield(:title))

- flash.each do |key, value|
    = value

Answer 1

1. = inserts HTML with escaped characters. Example:

   = javascript_include_tag("1", "2")
   

2. == inserts HTML without escaping. It is needed when you have already rendered HTML and you need to insert it to your layout directly. Example:

   == render 'footer'
   

Answer 2

From the documentation:

Output =

The equal sign tells Slim it's a Ruby call that produces output to add to the buffer.

Output without HTML escaping ==

Same as the single equal sign (=), but does not go through the escape_html method.

Update regarding HTML escaping:

First of all, what "html escape" means is this:

puts html_escape('is a > 0 & a < 10?')
# => is a &gt; 0 &amp; a &lt; 10?

Then, some reading about why/when you want to do it:

• Do I really need to encode '&' as '&'?
• http://text-symbols.com/html/encode/
• http://www.w3schools.com/html/html_entities.asp