Regex fun. Why doesn't this regex match my string?

Question

I'm debugging carrierwave. It's fun. I think the problem comes down to this:

Inside carrierwave_direct, there's this code:

if record.new_record? && record.send("has_#{attribute}_upload?") && record.key !~ record.send(attribute).key_regexp

The #key_regexp code is this:

  /\A#{store_dir}\/[a-f\d\-]+\/.+\.(?i)#{extension_regexp}(?-i)\z/

which evaluates to this when I am debugging:

record.send(attribute).key_regexp
/\Astories\/\/main_images\/[a-f\d\-]+\/.+\.(?i)(jpg|jpeg|gif|png)(?-i)\z/

My store_dir is this:

"stories/#{model.id}/main_images"

and I think there's a blank "/" section because model.id is nil.

The record.key is this:

"/stories/main_imagescache/20160319-1549-2202-5826/blueapronimage.jpg"

Why doesn't it currently match?

It looks like the regex has an extra slash and I'm not sure what this section is:

[a-f\d\-]+\/.+\.(?i)(jpg|jpeg|gif|png)(?-i)

Is it any number of letters between a-f, digit, or "-", then a "/", then any number of letters or numbers, then a "."....

What is the (?i)?

What are capture groups?

What is the (?-i)?

I think this is the problem:

record.key !~ /\Astories/
true

It should be false.

Answer 1

Look at this, it explains it:

[a-f\d\-]+            # Matches a-f, any digit, - (hyphen)
                      # ^ One or more times (+)
\/                    # Matches a /
.+                    # Matches any character one or more times
\.                    # Matches a . (dot)
(?i)                  # States that anything after this is case-insesitive
                      # ^ Inline Flag
(jpg|jpeg|gif|png)    # Selects file extension
                      # ^ (either jpg, jpeg, gif, or png)
(?-i)                 # Removes Inline Flag

That should explain what each one does.

Also check out this Live Demo. Your example does seem to match, maybe another part of your code is incorrect...