Question

I am receiving a JSON post into my Rails 3 application. I am then parsing each of the values and inserting them into the application database. It’s all working well but now I would like to modify the received values before inserting them into the database.

:subject => email_payload['subject']

As the above code shows, I am inserting the received value for ‘subject’ into the column named ‘subject’.

In the example above the received value is like this:

Results from Example Company - Surname/Firstname/[12345]

What I would like to do is strip everything out except the numerical value between the []. So the value that’s inserted into the database is simply:

12345

I can, presumably, just select anything from 0-9 but how do I add regex to the received string?

None of the following seem to work:

['subject.gsub!([0-9])']
['subject'.gsub!([0-9])]
['subject'].gsub!([0-9])

I’ve tested the Regex here http://rubular.com/r/AVFkm3A440

Answer 1

Since you are applying the .gsub() to the value returned by the hash key email_payload['subject'], the method belongs chained outside the closing ].

Your regular expression is missing its / delimiters. To capture the group as a whole, add a + as in /[^0-9]+/. The ^ will match all non-digit characters, and then .gsub() will replace them with an empty string. So the pattern below will mutate the key email_payload['subject'] in place

email_payload['subject'] = 'Results from Example Company - Surname/Firstname/[12345]'

email_payload['subject'].gsub!(/[^0-9]+/, '')
>> "12345"
# gsub!() has mutated the value:
puts email_payload['subject']
>> 12345