How do I make dynamic ids in Haml?

#item

creates a div with id="item"

.box#item

creates a div with class="box" and id="item"

.box#="item "+x

creates a div with class="box" and a comment '#="item"+x'

.box#
  ="item"+x

throws "Illegal element: classes and ids must have values."

How do I get set the id to a variable?

There are two ways:

The long form way (define the id as if it were a regular attribute):

.box{:id => "item_#{x}"}

produces this (x is what ever x.to_s evaluates to):

<div class="box" id="item_x">

The short form way:

.box[x]

produces the following assuming x is an instance of item:

<div class="box item" id="item_45">

See the HAML reference for more information.

You can set the id and class in HAML the following ways

1. The normal way

    .box.item#item
   

    <div id="item" class="box item"></div>
   

2. If you need to interpolation you can use this format

    .box{id: "item_#{123}", class: "item_#{123}"}
   

    <div id="item_123" class="box item_123"></div>
   

3. This format generates the class and id using the object reference

    # app/controllers/items_controller.rb 
    @item = Item.find(123)
   

    .box[@item]
   

    <div id="item_123" class="box item"></div>
   

4. If you need to prefix something

    .box[@item, :custom]
   

    <div id="custom_item_123" class="box custom_item"></div>
   

5. If you need a custom class and id generation you need to add the following method to model.

    class CrazyUser < ActiveRecord::Base
      def haml_object_ref
        "customized_item"
      end
    end
   

   And then you will get the customized class

    .box[@item]
   

    <div id="customized_item_123" class="box customized_item"></div>
   

Refer:

• http://haml.info/docs/yardoc/file.REFERENCE.html#object-reference-
• http://haml.info/docs/yardoc/file.REFERENCE.html