A purely-functional library for defining type-safe schemas for algebraic data types, providing free generators, SQL queries, JSON codecs, binary codecs, and migration from this schema definition.
Scalaz Schema defines a generic representation of algebraic data structures and combinators that turn such schema into a generic computation over arbitrary data. In other words, Scalaz Schema provides a way to express any computation that abstracts over the structure of data, such as:
- Codecs: given a serial format (binary, JSON, etc.) and the schema of a data structure (say, an ADT) we can derive a codec for that data structure and serial format.
- Data Generators: given any schema we can derive random data generators (eg. scalacheck's
Gen) that produce data satisfying that schema. - Schema/Data Migrations: since schemas are values, we can easily verify whether two versions of a schema are forward/backward compatible and provide a generic way to upgrade/downgrade data from one version of the schema to the other.
- Diffing/Patching: given a schema we can generically compute the difference between two pieces of data satisfying that schema. In the same spirit, we have generic way to apply patches to arbitrary data structures.
- Queries: knowing a schema, we can produce SQL queries to interact with a database that holds an instance of (the SQL version of) that schema.
| codecs | generators | migrations | diff/patch | queries | |
|---|---|---|---|---|---|
| xenomorph | ✓ | ✓ | ? | 𐄂 | 𐄂 |
| shapeless * | ✓ | ✓ | 𐄂 | ✓ | 𐄂 |
*: shapeless provides only the way to abstract over the structure of data, but several libraries build upon shapeless to provide the feature listed in the table.
Scalaz Schema shares ideas with @nuttycom's xenomorph library. The talk below presents its design.
An Haskell port of the ideas of xenomorph has also been implemented: haskell-schema.