Match optional pattern preceeded by random content

Question

I need to capture two groups in the following sentence, one is I, the other is optional

I want to match random optional field.

I tried the following approach, but it's not yielding expected result:

(I).*?(optional)?

Removing the round patenthesis around optional can match correctly, but since I need the second match, I can't do so.

(I).*?optional?

So how can I match both groups correctly? thanks!

Answer 1

The trick with your regex is that you need to group (and discard) anything leading up to optional that doesn't match optional.

Use negative look-around (with a ?: prepended so that the group isn't used for capture):

(I)(?:(?!optional).)*(optional)?.*