lode - v0.1.0

lode/type_

The Ecto type system, re-expressed without behaviours or parameterized types.

In Ecto a “type” is a module implementing cast/load/dump/equal? (plus the Ecto.Type / Ecto.ParameterizedType behaviours). Gleam has no behaviours, so a type is just a record of functions, parameterized by the Gleam type a it produces. Composite types (array, map) are ordinary functions over LodeType, and custom types (Enum, UUID) are ordinary constructors.

Types

FieldType

</>

A type-erased type that operates purely on Value. The schema and changeset layers are generic over a row type and can’t hold a heterogeneous list of LodeType(a) (each a differs per field), so they store this erased form.

  • cast: validate+normalize external input into a canonical, DB-ready Value
  • load: validate+normalize a database value into a canonical Value

Both produce a canonical Value (the result of casting then dumping), so the changeset can work entirely in Value-space while still enforcing the type.

pub type FieldType {
  FieldType(
    name: String,
    cast: fn(value.Value) -> Result(value.Value, Nil),
    load: fn(value.Value) -> Result(value.Value, Nil),
  )
}

Constructors

LodeType

</> 
pub type LodeType(a) {
  LodeType(
    name: String,
    cast: fn(value.Value) -> Result(a, Nil),
    load: fn(value.Value) -> Result(a, Nil),
    dump: fn(a) -> Result(value.Value, Nil),
    equal: fn(a, a) -> Bool,
  )
}

Constructors 

  • LodeType(
  name: String,
  cast: fn(value.Value) -> Result(a, Nil),
  load: fn(value.Value) -> Result(a, Nil),
  dump: fn(a) -> Result(value.Value, Nil),
  equal: fn(a, a) -> Bool,
)

    Arguments

    name

    Stable name used in error messages and (later) for SQL type mapping.

Values

cast

</> 
pub fn cast(
  of t: LodeType(a),
  value v: value.Value,
) -> Result(a, Nil)

Run the cast step.

dump

</> 
pub fn dump(
  of t: LodeType(a),
  value v: a,
) -> Result(value.Value, Nil)

Run the dump step.

equal

</> 
pub fn equal(of t: LodeType(a), left x: a, right y: a) -> Bool

Semantic equality for this type.

erase

</> 
pub fn erase(t: LodeType(a)) -> FieldType

Erase a typed LodeType(a) into a Value-only FieldType by composing cast/load with dump.

load

</> 
pub fn load(
  of t: LodeType(a),
  value v: value.Value,
) -> Result(a, Nil)

Run the load step.

simple

</> 
pub fn simple(
  name name: String,
  decode decode: fn(value.Value) -> Result(a, Nil),
  encode encode: fn(a) -> Result(value.Value, Nil),
) -> LodeType(a)

Build a type whose cast and load share the same conversion, with structural equality. This covers most primitive types.

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