Description

Use datomic with intention revealing names. Ease of use and sticking to datomic's principles are encouraged. Should work with datomic >= 0.8.3789.

Install

Add to your project.clj:

[datomico "0.2.0"]

Usage

Let's build a datomic entity type and start datomic with build-schema and start:

(ns models.user)
(require '[datomico.core :as dc])

; Define a model's database key once and don't think of it again while
; interacting with your model
(def model-namespace :user)

; Build schemas easily without needing to think of partitions and a number of
; internal schema attributes. Basically you don't have to pore over
; http://docs.datomic.com/schema.html
(def schema (dc/build-schema model-namespace
  [[:username :string]
  [:password :string]]))

; Starting in a repl is easy;  a uri, db and connection will be auto-generated
(ns user)
(require '[datomico.core :as dc])
(dc/start {:dynamic-vars true
           :schemas [models.user/schema]})

Let's create, update, delete and query entity types with create, update, delete and find-all:

(ns models.user)
; creates several helper functions that scope your database interaction to the model.
(dc/create-model-fns model-namespace)

(create {:username "dodo" :password "bird"})
; => {:username "dodo" :password "bird" :id 1024053}
(find-all {:username "dodo"})
; => ({:username "dodo" :password "bird" :id 1024053})
(find-first {:password "bird"})
; => {:username "dodo" :password "bird" :id 1024053}

(update 1024053 {:username "big"})
(dc/delete 1024053)

Transacting Batch Data

To transact data in batches, datomico provides *-tx corollaries to fns in datomico.action and datomico.model. These fns generate transaction data which can be batched and transacted as needed.

For this example, assume we're in a url model that has string attributes :name and :desc and a many ref with :tags. Let's create a new entity that associates itself with two existing entities "clojure" and "database". We'll use create's corollary create-tx to do this

(ns models.url
  (:require [datomico.db :as db]
            [datomic.model :as model]))

(def model-namespace :url)
(def find-first (partial model/find-first model-namespace))
(def create-tx (partial model/create-tx model-namespace))

(let [input {:name "http://datomic.com" :desc "DESC" :tags ["clojure" "database"]}
      new-map (create-tx (dissoc input :tags))]
  (->> (:tags input)
       (map #(find-first {:name %}))
       (map #(create-tx {:id (:db/id new-map) :tags (:id %)}))
       (cons new-map)
       db/transact!))

Note that create-tx provides :db/id with a tempid you can use to associate it to other entities in the same transaction.

Dynamic Binding

For actual production code, it is not recommended to use :dynamic-vars with datomico.core/start. Instead, you should be more explicit about handling your *db* and *connection* as :dynamic-vars incurs a performance penalty in exchange for convenience. For example, a ring app should start datomic with:

(dc/start {:uri "datomic:mem://my-app"
           :schemas [models.user/schema]})

Then, your ring app should use datomico's ring middleware to explicitly define *db* and *connection* for the duration of a web request:

(-> app datomico.db/wrap-datomic)

Look at wrap-datomic's implementation if not in a ring context.

TODO

• More tests!

Bugs/Issues

Please report them on github.

License

See LICENSE.TXT

Credits

• @relevance for fridays!
• @bobby for much of the initial abstraction - https://gist.github.com/3150938
• @boxxxie - for schema improvements
• @ravster - for tests

Links

• demonic - Datomic utils for testing, batch commits, schema definitions, and more
• adi - An Object/Map Based Syntax for Datomic
• Sample blog using datomico - Needs to be updated. Last known working commit - 50da3787e11608a98ed54220a371c7035ccdfa12.
• Sample pastebin using datomico - Needs to be updated. Last known working commit - 50da3787e11608a98ed54220a371c7035ccdfa12.