How to write if-condition in Haml?

Question

How to write if and if-else statements in Haml for a Ruby on Rails application?

bilash.saha · Accepted Answer · 2011-11-08T08:42:25.867

138

HAML is indentation based , and the parser can be tricky.You don't need to use "- end" in Haml. Use indentation instead.In Haml,a block begins whenever the indentation is increased after a Ruby evaluation command. It ends when the indentation decreases.Sample if else block as follows.

- if condition
  = something
- else
  = something_else

A practical example

- if current_user
  = link_to 'Logout', logout_path
- else
  = link_to 'Login', login_path

Edit : If you just want to use if condition then

 - if current_user
  = link_to 'Logout', logout_path

edited Nov 08 '11 at 08:42

answered Nov 06 '11 at 11:17

bilash.saha

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But how to use only if modifier – Thillai Narayanan Nov 08 '11 at 08:33
just use if like i have edited in the answer.no need to have end.The indentation will do the rest. – bilash.saha Nov 08 '11 at 08:42
An answer to your practical question: link_to_if http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to_if – Jeffrey LeCours Oct 09 '13 at 02:28
I wanted to have another non output statement inside the if like - if current_user - i = 5 and was wondering why it wasn't working though I've indented it! Finally realised the - has to be indented :) – msanjay Aug 19 '14 at 08:57
1

How to add `or` operator to the condition? – Joe Hany Apr 13 '16 at 17:22
Only thing confusing me about this answer, is how to have multiple lines in the condition statement with just a single '='. There doesn't seem any point to using the = if indenting will do it – PandaWood Jul 11 '16 at 14:18

score 20 · Answer 2 · edited Sep 20 '12 at 13:41

20

In haml two operators are used for ruby code.

= is used for ruby code which is evaluated and gets inserted into document.

Example:

= form_for @user

- is used for ruby code which is evaluated and NOT get inserted into document.

Example:

- if @user.signed_in?  
  = "Hi"  
- else  
  = "Please sign in!"

edited Sep 20 '12 at 13:41

Anne

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answered Sep 20 '12 at 13:18

Pratik Ganvir

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Please note you do not really need `=` if you want to output plain string like `Hi` or `Please sign in`. `=` is only necessary for evaluating Ruby, like `= "Hi, #{@user.name}"` – khustochka Sep 20 '12 at 13:40

score 9 · Answer 3 · answered Nov 06 '11 at 11:14

In haml, use the - (dash) to indicate a line is Ruby code. Furthermore, indention level indicates block level. Combine the two for if/else statements.

- if signed_in?
  %li= link_to "Sign out", sign_out_path
- else
  %li= link_to "Sign in", sign_in_path

is the same as the following code in ERB:

<% if signed_in? %>
  <li><%= link_to "Sign out", sign_out_path %></li>
<% else %>
  <li><%= link_to "Sign in", sign_in_path %></li>
<% end %>

Anton S. · Answer 4 · 2020-03-25T01:37:09.410

2

If you want to put condition inside your tag

%section{:class => "#{'new-class' if controller.action_name == 'index'}"}

UPDATE

Here is another variation

%nav(class="navbar"){class: content_for?(:navbar_class) ? yield(:navbar_class) : nil}

edited Mar 25 '20 at 01:37

answered May 13 '17 at 16:25

Anton S.

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How to write if-condition in Haml?

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