Calculating total karma for a user

[Brotakuu]

What would be the best way to calculate the total number of votes a user has received? (ie: tally all votes from posts a user created).

Would the best approach be to create a counter that increments everytime a vote is cast? Or is there a built in method that can tally the total?

[bouchard]

To sum all votes for posts for a particular user: `User.find(...).posts.map(&:votes_for).sum` To sum all votes for subtracted from votes against for a particular user, who created posts: `User.find(...).posts.map(&:plusminus).sum` If you're doing this often, it would be worthwhile to denormalize this to the User model.

[Brotakuu]

Thanks, that was exactly what I was looking for. I tried to search online for what you mean by denormalize this to the User model. Would you mind explaining or adding an example?

Do you mean create a method in the model like:

def get_karma
    return self.posts.map(&:votes_for).sum
end

[bouchard]

By denormalize, I mean you can store the computed value on the User model (if you have lots of posts, would be useful, but not necessary - just for performance reasons). By the way, you should generally name your methods with adjectives/nouns, not verbs/adverbs, in Ruby convention. A.k.a., not `get_karma`, but `karma`. Something like: ```ruby class User def votes_for_all_posts # Create an integer field `votes_for_all_posts` on User, and make sure Post has an index on `created_at`. if posts.order('created_at ASC').first.created_at > created_at v = posts.map(&:votes_for).sum write_attribute(:votes_for_all_posts, v) v else read_attribute(:votes_for_all_posts) end end end ```