View Decorators are Rails view partials that are discovered by a conventional file path based on the model name and attribute being accessed. The partial has access to the current record, the default value, as well as all other objects typically available in Rails views.
The following methods are available in a decorator’s render context on top of the typical Rails view context:
| Name | Description |
|---|---|
default |
The original, unmodified value returned directly from the model. |
record |
The full model instance. i.e. default is shorthand for (e.g.) record.name, record.email, etc. depending on the given decorator definition. |
To create a decorator for a User object’s name attribute, create a file named app/views/decorators/users/_name.html.erb.
<%# app/views/decorators/users/_name.html.erb %>
<span class="name">
<%= default %>
</span>
<% if record.created_at.present? %>
<span class="created-at">
(Created: <%= time_ago_in_words(record.created_at) %> ago)
</span>
<% end %>
Here’s an example of that exact decorator being applied to a User instance in an Item Table:
| user@example.com | |
| Name | John Smith (Created: 5 days ago) |
Since View Decorators are applied every time a value is displayed (note that Forms always use the raw value, never the decorated value), you may need to display a value differently depending on the context. For example, you may want to display the default value in an index view, and you may want a customized display value in a show view.
If this is required, simply use an if statement and inspect Rails’ provided controller_action method:
<%# app/views/decorators/users/_email.html.erb %>
<% if controller_action == 'index' %>
<%= default %>
<% else %>
<%= mail_to default %>
<% end %>