I have a DB field that is integer type and values are always 0 or 1. How do I grab the equivalent boolean value in ruby? such that when i do the following the check box is set appropriately:
<%= check_box_tag 'resend', @system_config.resend %>
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4 Answers
You could use the zero? method. It returns true if 0. If you need to backwards, you could easily negate it to !@system_config.resend.zero?. Or you could extend the Fixnum class, adding a to_b? method, since everything is open and extensible in dynamic languages.
class Integer
def to_b?
!self.zero?
end
end
Ruby API: http://ruby-doc.org/core/classes/Fixnum.html#M001050
6 Comments
rrevi
Thanks Jarret. Part of my solution was also to use the check_box_tag helper properly like so: <%= check_box_tag 'resend', @system_config.resend, @system_config.resend %>
Andrew Marshall
Note that there's also
nonzero? which may read better than !zero?.
Alexander Bird
I would very strongly recommend not adding functions to built-in classes. I come from a more javascript world where there are multiple times where that comes back to bite people, but more than just that: Everyone reading the code will know what
nonzero? function is, but would have no idea what to_b? is!
chesterbr
Just be careful with
nonzero? - it returns truthy and falsy values, but not true as zero? does (they are defined in different classes, see ruby-doc.org/core-1.9.3/Fixnum.html#method-i-zero-3F versus ruby-doc.org/core-1.9.3/Numeric.html#method-i-nonzero-3F
Fralcon
@chesterbr I agree. This just threw me for a loop right now. I looked up why
nonzero? did not return a boolean as most ruby predicate methods do and came upon this ticket debating getting this corrected bugs.ruby-lang.org/issues/9123. Seems not everyone agrees this is an issue so it unfortunately doesn't seem to be going anywhere. |
1 is your only truth value here. So you can get the boolean truth value with number == 1.
3 Comments
Simon B.
Maybe this could be worded more clearly. I almost thought you meant this to be ruby standard. The accepted answer seem to give a ruby-standard-compatible solution, that happens to also fit with the actual question.
Chuck
@Simon B.: I'm not sure what about my answer seems "non-standard" to you. Both the
== and zero? methods are standard Ruby. But it so happens that number == 1 reads more clearly than !number.zero? IMO.Simon B.
In ruby, both 0 and 1 are "truthy", so actually there's no chance to make any answer here both "standard" and answer the question. Sorry. Maybe I better to try to get this into the question text or title. Anyone coming here looking for "ruby-faithful type casting" from Fixnum to Boolean will otherwise get confused either way. Also, according to drawingablank.me/blog/ruby-boolean-typecasting.html is seems !! is the only ruby-faithful option. Which is not an option in the question above.
With Rails there's also ActiveModel::Type::Boolean.new.cast(value) which makes 0 false, non-zero true, [] true, {} true. Note that nil -> nil.
Comments
I had the same problem and dealt with it this way:
def to_boolean(var)
case var
when true, 'true', 1, '1'
return true
when false, 'false', 0, '0'
return false
end
end
This works with forms, databases and people who don't know Ruby. I found it to be useful especially with Rails, since parameters are often passed/interpreted as strings and I don't want to worry about that.
