Question

I have a simple problem, yet i am unable to solve this.
Either my string has a format ID: dddd, with the following regular expression:

/^ID: ([a-z0-9]*)$/

or as follows: ID: 1234 Status: 232, so with the following regular expression:

/^ID: ([a-z0-9]*) Status: ([a-z0-9]*)$/

Now i want to make one regular expression that can handle both. The first thing i came up with was this:

/^ID: ([a-z0-9]*)$|^ID: ([a-z0-9]*) Status: ([a-z0-9]*)$/

It matches, but i was looking into conditional regular expressions, and was thinking that something should be possible along the lines of (pseudo-codish)

if the string contains /Status:/
    /^ID: ([a-z0-9]*)$/
else
    /^ID: ([a-z0-9]*) Status: ([a-z0-9]*)$/

only, i can’t get this expressed correctly. I thought i should be using /?=/ but have no clue how.
Something like

/((?=Status)^ID: ([a-z0-9]*) Status: ([a-z0-9]*)$|^ID: ([a-z0-9]*)$/

but that doesn’t work.

Can you help?

Answer 1

You’re looking for ^ID: (\d+)(?: Status: (\d+))?$

edit:
Since the question is tagged Ruby it’s worth mentioning that according to both
this question and this flavour-comparison, Ruby doesn’t do conditional regex.

http://www.regular-expressions.info is a great source on the subject.