croma v0.4.0 Croma.Struct
Utility module to define structs and some helper functions.
Using this module requires to prepare modules that represent each struct field. Each of per-field module must provide the following members:
- required:
@type t
- required:
@spec validate(term) :: Croma.Result.t(t)
- optional:
@spec default :: t
Some helpers for defining such per-field modules are available.
- Wrappers of built-in types such as
Croma.String
,Croma.Integer
, etc. - Utility modules such as
Croma.SubtypeOfString
to define “subtypes” of existing types. - Ad-hoc module generators defined in
Croma.TypeGen
.
To define a struct, use
this module with a keyword list:
defmodule S do
use Croma.Struct, fields: [field1_name: Field1Module, field2_name: Field2Module]
end
Then the above code is converted to defstruct
along with @type t
.
This module also generates the following functions.
@spec new(Dict.t) :: Croma.Result.t(t)
@spec new!(Dict.t) :: t
@spec validate(term) :: Croma.Result.t(t)
@spec validate!(term) :: t
@spec update(t, Dict.t) :: Croma.Result.t(t)
@spec update!(t, Dict.t) :: t
Examples
iex> defmodule I do
...> @type t :: integer
...> def validate(i) when is_integer(i), do: {:ok, i}
...> def validate(_), do: {:error, {:invalid_value, [__MODULE__]}}
...> def default, do: 0
...> end
...> defmodule S do
...> use Croma.Struct, fields: [i: I]
...> end
...> S.validate([i: 5])
{:ok, %S{i: 5}}
...> S.validate(%{i: "not_an_integer"})
{:error, {:invalid_value, [S, I]}}
...> {:ok, s} = S.new([])
{:ok, %S{i: 0}}
...> S.update(s, [i: 2])
{:ok, %S{i: 2}}
...> S.update(s, %{"i" => "not_an_integer"})
{:error, {:invalid_value, [S, I]}}
Naming convention of field names (case of identifiers)
When working with structured data (e.g. JSON) from systems with different naming conventions,
it’s convenient to adjust the names to your favorite convention in this layer.
You can specify the acceptable naming schemes of data structures to be validated
by :accept_case
option of use Croma.Struct
.
nil
(default): Accepts only the given field names.:lower_camel
: Accepts both the given field names and their lower camel variants.:upper_camel
: Accepts both the given field names and their upper camel variants.:snake
: Accepts both the given field names and their snake cased variants.:capital
: Accepts both the given field names and their variants where all characters are capital.