How to check if a string is a valid date

Question

I have a string: \"31-02-2010\" and want to check whether or not it is a valid date. What is the best way to do it?

I need a method which which returns

Answer 1

Date.valid_date? *date_string.split('-').reverse.map(&:to_i)

Answer 2

Posting this because it might be of use to someone later. No clue if this is a "good" way to do it or not, but it works for me and is extendible.

class String

  def is_date?
  temp = self.gsub(/[-.\/]/, '')
  ['%m%d%Y','%m%d%y','%M%D%Y','%M%D%y'].each do |f|
  begin
    return true if Date.strptime(temp, f)
      rescue
       #do nothing
    end
  end

  return false
 end
end

This add-on for String class lets you specify your list of delimiters in line 4 and then your list of valid formats in line 5. Not rocket science, but makes it really easy to extend and lets you simply check a string like so:

"test".is_date?
"10-12-2010".is_date?
params[:some_field].is_date?
etc.

Answer 3

Another way to validate date:

date_hash = Date._parse(date.to_s)
Date.valid_date?(date_hash[:year].to_i,
                 date_hash[:mon].to_i,
                 date_hash[:mday].to_i)

Answer 4

require 'date'
begin
   Date.parse("31-02-2010")
rescue ArgumentError
   # handle invalid date
end

Answer 5

I'd like to extend Date class.

class Date
  def self.parsable?(string)
    begin
      parse(string)
      true
    rescue ArgumentError
      false
    end
  end
end

example

Date.parsable?("10-10-2010")
# => true
Date.parse("10-10-2010")
# => Sun, 10 Oct 2010
Date.parsable?("1")
# => false
Date.parse("1")
# ArgumentError: invalid date from (pry):106:in `parse'

Answer 6

Here is a simple one liner:

DateTime.parse date rescue nil

I probably wouldn't recommend doing exactly this in every situation in real life as you force the caller to check for nil, eg. particularly when formatting. If you return a default date|error it may be friendlier.