What does the Ruby operator == do in this case?

Question

I'm currently looking at a piece of code from the excellent Rails-composer and I don't understand what the Embedded Ruby in the 3rd line does:

<% flash.each do |name, msg| %>
  <% if msg.is_a?(String) %>
    <div class="alert alert-<%= name == :notice ? "success" : "error" %>">
      <a class="close" data-dismiss="alert">&#215;</a>
      <%= content_tag :div, msg, :id => "flash_#{name}" %>
    </div>
  <% end %>
<% end %>

I've looked at the Ruby documentation with no luck so far. Once I understand how this code works I'd like to extend it to support all levels of flash[] messages.

possible duplicate of [How do I use the conditional operator (? :) in Ruby?](http://stackoverflow.com/questions/4252936/how-do-i-use-the-conditional-operator-in-ruby) — Andrew Marshall, Jan 22 '13 at 18:16
Maybe this links is useful: https://stackoverflow.com/questions/2151410/c-sharp-auto-highlight-text-in-a-textbox-control — Filipe Freire, Jul 10 '17 at 11:35

score 6 · Accepted Answer · answered Jan 22 '13 at 18:09

6

It's the Ternary Operator.

(condition) ? "true value" : "false value"

It's saying if name == :notice use "success" otherwise "error".

answered Jan 22 '13 at 18:09

Austin Brunkhorst

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The link to Wikipedia doesn't want to work so replace `?` with `%3F` in the URL. – Austin Brunkhorst Jan 22 '13 at 18:14

Andrzej Gis · Answer 2 · 2013-01-22T18:30:46.843

2

This line

result = (name == :notice ? "success" : "error")

Can be tanslated to:

result =""
if(name == :notice)
{
 result = "success"
}
else
{
 result = "error"
}

In your case the result is not a variable, but it's value is pasted to html.

EDIT

I'd like to extend it to support all levels of flash[] messages.

This operator is usually used just for simple true false condition, though if you really want you can use it like that:

name == :notice ? "success" : name == :error ? "error" : "something else"

Consider using this instead (more readable)

if name == :notice
 "success"
elsif name == :error
 "error"
else
 "something else"
end

edited Jan 22 '13 at 18:30

answered Jan 22 '13 at 18:15

Andrzej Gis

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Hi @gisek, I wish I could have awared 2 answers to my question. Really appreciated yours as well. – Francis Ouellet Jan 22 '13 at 22:44
@FrancisOuellet I'm glad I could help :) – Andrzej Gis Jan 23 '13 at 17:56

Pedro Tavares · Answer 3 · 2013-01-22T22:38:31.807

1

That code changes the div class dynamically. It checks for :notice and the div class will get:

"alert alert-success"
"alert alert-error"

depending of :notice result.

edited Jan 22 '13 at 22:38

answered Jan 22 '13 at 18:21

Pedro Tavares

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6
17

score 0 · Answer 4 · answered Jan 22 '13 at 18:11

It's displaying the contents of the flash. Each key-value pair of the flash is displayed as a separate div, with the class of the div depending on the key.

Line 3 is adding a class of alert-success or alert-failure depending on whether the key is :notice or not

What does the Ruby operator == do in this case?

4 Answers4