glite - v0.5.0

glite/decode

Decoders that turn a result row into a typed value.

If you also use gleam/dynamic/decode, import this module under another name, such as import glite/decode as row.

import glite/decode

let user = {
  use id <- decode.element(0, decode.int)
  use name <- decode.element(1, decode.text)
  use email <- decode.element(2, decode.optional(decode.text))
  decode.success(User(id:, name:, email:))
}

Types

RowDecoder

opaque </>

Decodes one row, a list of column values.

pub opaque type RowDecoder(a)

ValueDecoder

</>

Decodes one column value. The error is a short description.

pub type ValueDecoder(a) =
  fn(value.Value) -> Result(a, String)

Values

blob

</> 
pub fn blob(value: value.Value) -> Result(BitArray, String)

Binary data. Text is accepted too, as its UTF-8 bytes, because SQLite doesn’t always say which of the two a value is.

bool

</> 
pub fn bool(value: value.Value) -> Result(Bool, String)

A boolean stored as the integer 0 or 1.

element

</> 
pub fn element(
  index: Int,
  decoder: fn(value.Value) -> Result(a, String),
  next: fn(a) -> RowDecoder(b),
) -> RowDecoder(b)

Decode the column at index, counting from 0, then carry on with next. Made for use.

fail

</> 
pub fn fail(message: String, at column: Int) -> RowDecoder(a)

A decoder that always fails with message, reported at column. Use it in then for a value no decoder should accept.

float

</> 
pub fn float(value: value.Value) -> Result(Float, String)

A float.

int

</> 
pub fn int(value: value.Value) -> Result(Int, String)

An integer.

map

</> 
pub fn map(
  decoder: RowDecoder(a),
  with f: fn(a) -> b,
) -> RowDecoder(b)

Change a decoded value with f.

let name_length = decode.map(name_decoder, string.length)

optional

</> 
pub fn optional(
  decoder: fn(value.Value) -> Result(a, String),
) -> fn(value.Value) -> Result(option.Option(a), String)

NULL becomes None; anything else goes through decoder.

raw

</> 
pub fn raw(value: value.Value) -> Result(value.Value, String)

The value as it is.

run

</> 
pub fn run(
  decoder: RowDecoder(a),
  row: List(value.Value),
  at row_index: Int,
) -> Result(a, error.Error)

Run a decoder on one row. row is the row’s position in its result, used in the error.

success

</> 
pub fn success(value: a) -> RowDecoder(a)

Finish a decoder with a value.

text

</> 
pub fn text(value: value.Value) -> Result(String, String)

Text.

then

</> 
pub fn then(
  decoder: RowDecoder(a),
  next: fn(a) -> RowDecoder(b),
) -> RowDecoder(b)

Decode the row with decoder, then decode the same row again with the decoder next picks from the result. For rows whose shape depends on a column, such as a kind column that says which other columns are set.

use kind <- decode.then(kind_decoder)
case kind {
  "circle" -> circle_decoder
  _ -> square_decoder
}
✨ Search Document