It’s a bit of a gray area where cannabis isn’t legalized, but Spanish privacy laws allow it in social clubs whether you’d like to view it as a loophole or not. You’re encouraged to consume at the club rather than taking it home just as a precaution of anything happening in transit. That being said, plenty of people smoke outdoors throughout the city because Catalonia tends to be more lax.
EDIT: I forgot to add that most social clubs will charge a membership fee. Some will be for a year, some are like three or six months. If you’re there for a bit, look at it as you’re buying a smoke spot. Nothing against bringing cannabis from another club if a different spot has better glass/amenities. I’d recommend reaching out to them on IG first since some have a bit of a vetting process if they’re not referral only.