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How to check if a string is a year

Ruby / RoR Usage - Year is a string in Model / View. How can I check that a user-entered string is a valid gregorian graphic year?

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With a bit of feat / regex magic, something like the following will allow you to check not only if a string is numeric (first criteria for a valid year), but also if it falls within a specific range of years:

def is_valid_year?(date_str, start=1900, end=2099)
  date_str.grep(/^(\d)+$/) {|date_str| (start..end).include?(date_str.to_i) }.first
end


The above function will return nil

for any string with non-numeric characters, false

for those that are numeric but outside the provided range, and true

for valid strings, the year.

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Seems like a more direct question: how do you validate that the user is entering a string that matches the number between 1582 and 2500 (say). You can do it like this:

 date_string.scan(/\D/).empty? and (1582..2500).include?(date_string.to_i)


so you can choose which is a reasonable year too, for example 800 is really a valid answer in your application? or 3000?

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Here's one way to do it:

Date.strptime(date_str, "%Y").gregorian?

Note that this will throw an exception if the string is in an unexpected format. Another (more forgiving) option:

Date.new(date_str.to_i).gregorian?
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@Rcoder's accepted answer won't work as I tested on rails 4+, I made another simple one.

def is_valid_year? year
  return false if year.to_i.to_s != year
  year.strip.to_i.between?(1800, 2999)
end

On the first line taking no characters, you can also change the range as you want

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Date.parse(string_of_date).gregorian?

Also, check out the documentation for the Date class .

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Wanting to parse an integer from a string is a fairly common question in Ruby. Probably because there is no perfect approach. Maybe he deserves his tag!

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