Error while 2 sequential writes in 1 transaction

[dbushenko]

I have following function

(defn create-user! [ email password db]
  (c/with-write-transaction [db tx]
    (let [encrypted-password (p/encrypt password)
          next-user-id (inc (c/get-at tx [:counters :user-id]))
          user {:email email
                :password-hash encrypted-password}]
      (c/merge-at tx [:users] {next-user-id user})
      (c/assoc-at tx [:counters :user-id] next-user-id))))

As you see I have one read and two writes within one transaction. But only the last write occurs. I expect that both writes should occur.

[dscarpetti]

Transactions are like (and implemented by) standard maps which contain uncommitted database modifications. When you change something a new transaction is returned, but the old transaction is unmodified. To make multiple changes to a transaction, you need to thread the transaction through multiple transformations, like so:

(-> tx
    (c/merge-at [:users] {next-user-id user})
    (c/assoc-at [:counters :user-id] next-user-id)))))

[dbushenko]

This is beautful solution which is totally not obvious :-) Please document that somehow

[dscarpetti]

Thank you for the feedback. I added an FAQ section to the README with examples based on our discussion here and in #9. Let me know if you think I should include anything else.