This may seem a minor issue, but I think it's worth a bit of
discussion to get it right. Let me start with the use case that led
me smack into the issue.
Start with some model that has a boolean field that can be nil/null.
Create a view with a form that uses a select box to set the field's
value, and set :include_blank => true. The obvious assumption is that
if you select blank (as opposed to Yes/1/true or No/0/false), the
field value will be saved as nil/null. Not so - it is saved as 0/
false. This has the weird behavior of the select box showing the
false choice when you select blank and get bounced back for a second
try at the form.
create_table :widgets do |t|
t.string :name
t.boolean :fancy
end
w = Widget.create(:name => "weather", :fancy => true)
w.fancy # => true
w.update_attributes(:fancy => nil)
w.fancy # => nil
w.update_attributes(:fancy => "")
w.fancy # => false
It's not too much trouble to patch ActiveRecord to change it so that
setting a boolean field to a blank string gets saved as NULL in the
database instead of 0. The question is: what is the desired
behavior? More specifically, when should the value be coerced, with
special consideration to the case when the field doesn't allow a nil/
NULL value?
I think the answer is that blank values should always be coerced to
nil in memory, even when the field is created with :null => false.
This is consistent with how integer fields are handled. You can have
a nil value in memory, and the db will barf when you try and save it
as NULL. AR expects you to use a validation to catch that and give
the user another shot at the form. However... there is what looks to
me like a bug in AR where assigning a blank-but-not-empty string to an
integer field has a different result from assigning an empty string or
nil. An empty string is coerced to nil, but a string of one or more
whitespace characters is coerced to 0. It's also easy to fix it so
that all blank strings are coerced to 0, and I think that would be the
best thing to do. But I wonder if anyone out there might be relying
on this behavior. There are only 2 tests that break when this change
is made (in validations_test.rb).
By the way, strings representing integers are coerced to their correct
values, but non-numeric objects like arrays and hashes are coerced to
1. WTF? Why is that useful?
I was going to create a ticket with a patch for this stuff to refer
to, but the code is sitting on a computer at work so that won't happen
until the morning (sorry, Pratik).
To summarize:
I propose that all blank strings should be coerced to nil, for both
boolean and integer fields. Any issues with that? Anyone know if
they are relying on that behavior?
--
Josh Susser
http://blog.hasmanythrough.com
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