differences.md

Differences from Toucan 1

Models are now just plain keywords

defmodel is no longer needed

In Toucan 2, a model is usually just a plain keyword, or even a plain string table name, or anything custom that implements table-name. As such, there is no need to define model classes with defmodel. Usually you decide that some namespaced keyword corresponds to some table in your database and go from there, implementing methods to customize its behavior as need. Usually you'll want to implement table-name, unless the name portion of the keyword matches the table name exactly:

(m/defmethod t2/table-name :models/user
  [_model]
  "core_user")

The optional toucan2-toucan1 compatibility layer provides a defmodel macro that mostly matches the syntax of the old defmodel and automatically creates an implementation of table-name for you, and derives that model from :toucan1/model (to implement other special backwards-compatibility behavior).

IModel protocol removed

Models are no longer invokeable

models/add-type! and models/types

toucan.models/add-type! has no direct equivalent; just define a map of

column-name -> direction -> transform-fn

somewhere, like this:

(def json-xform
  {:in  json-in
   :out json-out-with-keywordization})

toucan.models/types has been replaced with toucan2.core/transforms, which provides similar functionality but is much more consistent in applying it. Example:

;; define the transform
(m/defmethod t2/transforms ::my-model
  [_model]
  {:some-field json-xform})

Note that nothing is stopping you from defining the transforms inline in the body of transforms itself; you can also define common transforms, and derive models from them.

transforms automatically merges all transforms maps for all matching methods; so you can define lots of common transforms this way and build models that use several of them. See documentation for more details. (TODO)

Hydrate is now a multimethod

'Simple' methods

toucan.models/primary-key is replaced with primary-keys

do-pre-update etc removed

with-temp syntax; with-temp* removed

define-before-insert, etc.

define-property! -- derive model

hydration-keys => t2/model-for-automagic-hydration

toucan.db/*db-connection* is now current *connectable* (TODO: not sure if this will be renamed)

toucan.db/connection removed

toucan.db/connection is defines something you can use to get a java.sql.Connection, for example a database details map or a javax.sql.DataSource; it was meant to be used with something like clojure.java.jdbc/with-db-connection, which uses with-open under the hood, or clojure.java.jdbc/get-connection in combination with with-open. Toucan 2 connectables handle their own lifecycle in their implementations of do-with-connection so you should not be using with-open yourself.

No need to flush hydration key caches