Validate date strings in Ruby with multiple accepted formats? - ruby-on-rails

Question

I have some strings that might or might not be dates like:
"Hello World", "Sept 12, 2013", "Hello World Sept 12"
In this case, I'd like only the second one to be considered a proper date.
So far, I have been using Date.parse and the Chronic gem but they very lenient and convert strings like "a a" or "12-UNKN/34/OWN1" into acceptable dates.
For example:
Date.parse '12-UNKN/34/OWN1'
would return:
Tue, 12 Nov 2013
So, I am trying to restrict the accepted formats to a set of formats I can control:
09/12/2013
9/12/2013
9/12/13
09-12-2013
9-12-2013
9-12-13
and some formats with text inside like:
Sept 9, 2013 - with or without the coma, accepting Sep, Sept or September and with or without a dot after the month name, covering things like:
Sept. 9, 2013
Sept 09, 2013
Sept. 09, 2013
September 9, 2013
September 09, 2013
Any suggestion on a good way to do this in Ruby, either pure Ruby or with Rails?

Answer 1

I'll take a stab at this and elaborate on my comment. Separating the date from the other string allows you to validate the date in multiple formats before handing it off to Chronic:
validates_format_of :date, with: /\d{2,4}[-/]\d{1,2}[-/]\d{1,4}/, on: :create
That should handle most of the date formats you described.
However, a big issue is you won't know if someone is submitting a date in the US format or non-US format.
The bigger issue is know what part of the title string is in fact a date, and that would either be a more complicated regular expression, or make it easy on yourself and make it a separate field. You're getting somewhat close to trying to parse natural language which isn't cut and dry by any means.

Answer 2

Try something like this
validate :validate_some_date
private
def validate_some_date
errors.add("Created at date", "is invalid.") unless [
date_case_one,
date_case_two,
date_case_three
].all?
end
def date_case_one
# some regex
end
def date_case_two
# some regex
end
def date_case_three
# some regex
end