Creating Checkboxes
Checkboxes are mostly simple. They can be checked or not checked, and Rails maps their contents to a boolean value transparently. This simple request for a checkbox:
<%= f.check_box :can_send_email %>
yields this bit of HTML:
<input id="person_can_send_email" name="person[can_send_email]" type="checkbox" value="1" /><input name="person[can_send_email]" type="hidden" value="0" />
Thatâs a little more complicated than expected, though. Why is there a second
input
element of type hidden
? Itâs another Rails workaround, providing a default value in case
the checkbox isnât checked:
Since HTTP standards say that unchecked checkboxes donât post anything, we add a hidden value with the same name as the checkbox as a workaround.[1]
If the checkbox is checked, that value will go through. If not, the value of the hidden input with the same name will go through.
The check_box
method has a few more tricks to offer.
As was possible with the text fields, you can specify additional attributesâperhaps
class
for CSS styling?âwith named
parameters:
<%= f.check_box :can_send_email, :class => 'email'
%>
This will produce a checkbox with a class
attribute:
<input class="email
" id="person_can_send_email" name="person[can_send_email]"
type="checkbox" value="1" /><input name="person[can_send_email]" type="hidden"
value="0" />
You can also specify that the box should be checked if you want, which will override the value that comes into the form from the underlying object. Use this with ...
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